Add BluetoothSerial library (#1144)

* Add BluetoothSerial library

A simple UART to Classical Bluetooth bridge for ESP32

* Create README.md

* Fix typos

* Replace deprecated header and small fixes

* Add coexistence with BLE

* Add missing semicolon

libraries/BluetoothSerial/src/BluetoothSerial.h

@@ -0,0 +1,56 @@
+// Copyright 2018 Evandro Luis Copercini
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef _BLUETOOTH_SERIAL_H_
+#define _BLUETOOTH_SERIAL_H_
+
+#include "sdkconfig.h"
+
+#if defined(CONFIG_BT_ENABLED) && defined(CONFIG_BLUEDROID_ENABLED)
+
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "esp_bt.h"
+
+#include "Arduino.h"
+#include "Stream.h"
+
+class BluetoothSerial: public Stream
+{
+    public:
+
+        BluetoothSerial(void);
+        ~BluetoothSerial(void);
+
+        bool begin(String localName=String());
+        int available(void);
+        int peek(void);
+        int read(void);
+        size_t write(uint8_t c);
+        size_t write(const uint8_t *buffer, size_t size);
+        void flush();
+        void end(void);
+
+    private:
+        String local_name;
+
+};
+
+#endif
+
+#endif