Docs: Initial documentation structure using Sphinx (#5355)

This PR is the initial documentation structure including the basic information about the project and Sphinx configuration.

####CONTENTS:
- Getting Started
- Installing
- Boards
- Libraries
- Library Builder
- Tutorials
- ESP-IDF as Component
- OTA Web Update
- makeEspArduino
- Troubleshooting
- Contributing

This PR also changes the README.md.

docs/source/api/bluetooth.rst

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+#############
+Bluetooth API
+#############

docs/source/api/deepsleep.rst

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+##########
+Deep Sleep
+##########

docs/source/api/espnow.rst

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+#######
+ESP-NOW
+#######
+
+ESP-NOW is a fast, connectionless communication technology featuring a short packet transmission.
+ESP-NOW is ideal for smart lights, remote control devices, sensors and other applications. 
+
+Example
+-------
+
+Resources
+---------
+
+* `ESP-NOW`_ (User Guide)
+
+.. _ESP-NOW: https://www.espressif.com/sites/default/files/documentation/esp-now_user_guide_en.pdf

docs/source/api/gpio.rst

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+####
+GPIO
+####

docs/source/api/rainmaker.rst

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+#########
+RainMaker
+#########

docs/source/api/reset_reason.rst

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+############
+Reset Reason
+############

docs/source/api/wifi.rst

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+#########
+Wi-Fi API
+#########
+
+About
+-----
+
+The Wi-Fi API provides support for the 802.11b/g/n protocol driver. This API includes:
+
+* Station mode (STA mode or Wi-Fi client mode). ESP32 connects to an access point
+
+* AP mode (aka Soft-AP mode or Access Point mode). Devices connect to the ESP32
+
+* Security modes (WPA, WPA2, WEP, etc.)
+
+* Scanning for access points
+
+Working as AP
+*************
+
+In this mode, the ESP32 is configured as an Access Point (AP) and it's capable of receiving incoming connections from other devices (stations) by providing
+a Wi-Fi network.
+
+.. figure:: ../_static/wifi_esp32_ap.png
+    :align: center
+    :width: 520
+    :figclass: align-center
+
+This mode can be used for serving a HTTP or HTTPS server inside the ESP32, for example.
+
+Working as STA
+**************
+
+The STA mode is used to connect the ESP32 to a Wi-Fi network, provided by an Access Point.
+
+.. figure:: ../_static/wifi_esp32_sta.png
+    :align: center
+    :width: 520
+    :figclass: align-center
+
+If you need to connect your project to the Internet, this is the mode you are looking for.
+
+API Description
+---------------
+
+Here is the description about the WiFi API.
+
+WiFiAP
+------
+
+The ``WiFiAP`` is used to configure and manage the Wi-Fi as an Access Point. This is where you can find the related functions for the AP.
+
+Basic Usage
+***********
+
+To start the Wi-Fi as an Access Point.
+
+.. code-block:: arduino
+
+    WiFi.softAP(ssid, password);
+
+Please see the full WiFiAP example in: `ap example`_.
+
+AP Configuration
+----------------
+
+softAP
+******
+
+Use the function ``softAP`` to configure the Wi-Fi AP characteristics:
+
+.. code-block:: arduino
+
+    bool softAP(const char* ssid, const char* passphrase = NULL, int channel = 1, int ssid_hidden = 0, int max_connection = 4, bool ftm_responder = false);
+
+Where:
+
+* ``ssid`` sets the Wi-Fi network SSID.
+* ``passphrase`` sets the Wi-Fi network password. If the network is open, set as ``NULL``. 
+* ``channel`` configures the Wi-Fi channel.
+* ``ssid_hidden`` sets the network as hidden.
+* ``max_connection`` sets the maximum number of simultaneous connections. The default is 4.
+* ``ftm_responder`` sets the Wi-Fi FTM responder feature. **Only for ESP32-S2 and ESP32-C3 SoC!**
+
+Return ``true`` if the configuration was successful.
+
+softAPConfig
+************
+
+Function used to configure the IP as static (fixed) as well as the gateway and subnet.
+
+.. code-block:: arduino
+
+    bool softAPConfig(IPAddress local_ip, IPAddress gateway, IPAddress subnet);
+
+Where:
+
+* ``local_ip`` sets the local IP address.
+* ``gateway`` sets the gateway IP.
+* ``subnet`` sets the subnet mask.
+
+The function will return ``true`` if the configuration is successful.
+
+AP Connection
+-------------
+
+softAPdisconnect
+****************
+
+Function used to force the AP disconnection.
+
+.. code-block:: arduino
+
+    bool softAPdisconnect(bool wifioff = false);
+
+Where:
+
+* ``wifioff`` sets the Wi-Fi off if ``true``.
+
+The function will return ``true`` if the configuration is successful.
+
+
+softAPgetStationNum
+*******************
+
+This function returns the number of clients connected to the AP.
+
+.. code-block:: arduino
+
+    uint8_t softAPgetStationNum();
+
+softAPIP
+********
+
+Function to get the AP IPv4 address.
+
+.. code-block:: arduino
+
+    IPAddress softAPIP();
+
+The function will return the AP IP address in ``IPAddress`` format.
+
+softAPBroadcastIP
+*****************
+
+Function to get the AP IPv4 broadcast address.
+
+.. code-block:: arduino
+
+    IPAddress softAPBroadcastIP();
+
+The function will return the AP broadcast address in ``IPAddress`` format.
+
+softAPNetworkID
+***************
+
+Get the softAP network ID.
+
+.. code-block:: arduino
+
+    IPAddress softAPNetworkID();
+
+The function will return the AP network address in ``IPAddress`` format.
+
+softAPSubnetCIDR
+****************
+
+Get the softAP subnet CIDR.
+
+.. code-block:: arduino
+
+    uint8_t softAPSubnetCIDR();
+
+softAPenableIpV6
+****************
+
+Function used to enable the IPv6 support.
+
+.. code-block:: arduino
+
+    bool softAPenableIpV6();
+
+The function will return ``true`` if the configuration is successful.
+
+softAPIPv6
+**********
+
+Function to get the IPv6 address.
+
+.. code-block:: arduino
+
+    IPv6Address softAPIPv6();
+
+The function will return the AP IPv6 address in ``IPv6Address`` format.
+
+softAPgetHostname
+*****************
+
+Function to get the AP hostname.
+
+.. code-block:: arduino
+
+    const char * softAPgetHostname();
+
+softAPsetHostname
+*****************
+
+Function to set the AP hostname.
+
+.. code-block:: arduino
+
+    bool softAPsetHostname(const char * hostname);
+
+Where:
+
+* ``hostname`` sets the device hostname.
+
+The function will return ``true`` if the configuration is successful.
+
+
+softAPmacAddress
+****************
+
+Function to define the AP MAC address.
+
+.. code-block:: arduino
+
+    uint8_t* softAPmacAddress(uint8_t* mac);
+
+Where:
+
+* ``mac`` sets the new MAC address.
+
+Function to get the AP MAC address.
+
+.. code-block:: arduino
+
+    String softAPmacAddress(void);
+
+softAPSSID
+**********
+
+Function to get the AP SSID.
+
+.. code-block:: arduino
+
+    String softAPSSID(void) const;
+
+Returns the AP SSID.
+
+WiFiSTA
+-------
+
+The ``WiFiSTA`` is used to configure and manage the Wi-Fi as Station. The related functions for the STA are here.
+
+Basic Usage
+***********
+
+The following code shows the basic usage of the WifiSTA functionality.
+
+.. code-block:: arduino
+
+    WiFi.begin(ssid, password);
+
+Where the ``ssid`` and ``password`` are from the network you want to connect the ESP32.
+
+To check if the connection is successful, you can use:
+
+.. code-block:: arduino
+
+    while (WiFi.status() != WL_CONNECTED) {
+        delay(500);
+        Serial.print(".");
+    }
+
+After a successful connection, you can print the IP address given by the network.
+
+.. code-block:: arduino
+
+    Serial.println("IP address: ");
+    Serial.println(WiFi.localIP());
+
+Please see the full example of the WiFiSTA in: `sta example`_.
+
+STA Configuration
+-----------------
+
+begin
+*****
+
+- Functions ``begin`` are used to configure and start the Wi-Fi.
+
+.. code-block:: arduino
+
+    wl_status_t begin(const char* ssid, const char *passphrase = NULL, int32_t channel = 0, const uint8_t* bssid = NULL, bool connect = true);
+
+Where:
+
+* ``ssid`` sets the AP SSID.
+* ``passphrase`` sets the AP password. Set as ``NULL`` for open networks.
+* ``channel`` sets the Wi-Fi channel.
+* ``uint8_t* bssid`` sets the AP BSSID.
+* ``connect`` sets ``true`` to connect to the configured network automatically.
+
+.. code-block:: arduino
+
+    wl_status_t begin(char* ssid, char *passphrase = NULL, int32_t channel = 0, const uint8_t* bssid = NULL, bool connect = true);
+
+Where:
+
+* ``ssid`` sets the AP SSID.
+* ``passphrase`` sets the AP password. Set as ``NULL`` for open networks.
+* ``channel`` sets the Wi-Fi channel.
+* ``bssid`` sets the AP BSSID.
+* ``connect`` sets ``true`` to connect to the configured network automatically.
+
+Function to start the connection after being configured.
+
+.. code-block:: arduino
+
+    wl_status_t begin();
+
+config
+******
+
+Function ``config`` is used to configure Wi-Fi. After configuring, you can call function ``begin`` to start the Wi-Fi process.
+
+.. code-block:: arduino
+
+    bool config(IPAddress local_ip, IPAddress gateway, IPAddress subnet, IPAddress dns1 = (uint32_t)0x00000000, IPAddress dns2 = (uint32_t)0x00000000);
+
+Where:
+
+* ``local_ip`` sets the local IP.
+* ``gateway`` sets the gateway IP.
+* ``subnet`` sets the subnet mask.
+* ``dns1`` sets the DNS.
+* ``dns2`` sets the DNS alternative option.
+
+The function will return ``true`` if the configuration is successful.
+
+The ``IPAddress`` format is defined by 4 bytes as described here:
+
+.. code-block:: arduino
+
+    IPAddress(uint8_t first_octet, uint8_t second_octet, uint8_t third_octet, uint8_t fourth_octet);
+
+Example:
+
+.. code-block:: arduino
+
+    IPAddress local_ip(192, 168, 10, 20);
+
+See the ``WiFiClientStaticIP.ino`` for more details on how to use this feature.
+
+STA Connection
+--------------
+
+reconnect
+*********
+
+Function used to reconnect the Wi-Fi connection.
+
+.. code-block:: arduino
+
+    bool reconnect();
+
+disconnect
+**********
+
+Function to force disconnection.
+
+.. code-block:: arduino
+
+    bool disconnect(bool wifioff = false, bool eraseap = false);
+
+Where:
+
+* ``wifioff`` use ``true`` to turn the Wi-Fi radio off.
+* ``eraseap`` use ``true`` to erase the AP configuration from the NVS memory.
+
+The function will return ``true`` if the configuration is successful.
+
+isConnected
+***********
+
+Function used to get the connection state.
+
+.. code-block:: arduino
+
+    bool isConnected();
+
+Return the connection state.
+
+setAutoConnect
+**************
+
+Function used to set the automatic connection.
+
+.. code-block:: arduino
+
+    bool setAutoConnect(bool autoConnect);
+
+Where:
+
+* ``bool autoConnect`` is set to ``true`` to enable this option.
+
+getAutoConnect
+**************
+
+Function used to get the automatic connection setting value.
+
+.. code-block:: arduino
+
+    bool getAutoConnect();
+
+The function will return ``true`` if the setting is enabled.
+
+setAutoReconnect
+****************
+
+Function used to set the automatic reconnection if the connection is lost.
+
+.. code-block:: arduino
+
+    bool setAutoReconnect(bool autoReconnect);
+
+Where:
+
+* ``autoConnect`` is set to ``true`` to enable this option.
+
+getAutoReconnect
+****************
+
+Function used to get the automatic reconnection if the connection is lost.
+.. code-block:: arduino
+
+    bool getAutoReconnect();
+
+    The function will return ``true`` if this setting is enabled.
+
+WiFiMulti
+---------
+
+The ``WiFiMulti`` allows you to add more than one option for the AP connection while running as a station.
+
+To add the AP, use the following function. You can add multiple AP's and this library will handle the connection.
+
+.. code-block:: arduino
+
+    bool addAP(const char* ssid, const char *passphrase = NULL);
+
+After adding the AP's, run by the following function.
+
+.. code-block:: arduino
+
+    uint8_t run(uint32_t connectTimeout=5000);
+
+To see how to use the ``WiFiMulti``, take a look at the ``WiFiMulti.ino`` example available.
+
+WiFiScan
+--------
+
+To perform the Wi-Fi scan for networks, you can use the following functions:
+
+Start scan WiFi networks available.
+
+.. code-block:: arduino
+
+    int16_t scanNetworks(bool async = false, bool show_hidden = false, bool passive = false, uint32_t max_ms_per_chan = 300, uint8_t channel = 0);
+
+Called to get the scan state in Async mode.
+
+.. code-block:: arduino
+
+    int16_t scanComplete();
+
+Delete last scan result from RAM.
+
+.. code-block:: arduino
+
+    void scanDelete();
+
+Loads all infos from a scanned wifi in to the ptr parameters.
+
+.. code-block:: arduino
+
+    bool getNetworkInfo(uint8_t networkItem, String &ssid, uint8_t &encryptionType, int32_t &RSSI, uint8_t* &BSSID, int32_t &channel);
+
+To see how to use the ``WiFiScan``, take a look at the ``WiFiScan.ino`` example available.
+
+Examples
+--------
+
+.. _ap example:
+
+Wi-Fi AP Example
+****************
+
+.. literalinclude:: ../../../libraries/WiFi/examples/WiFiAccessPoint/WiFiAccessPoint.ino
+    :language: arduino
+
+.. _sta example:
+
+Wi-Fi STA Example
+*****************
+
+.. literalinclude:: ../../../libraries/WiFi/examples/WiFiClient/WiFiClient.ino
+    :language: arduino
+
+References
+----------