Documentation rework - add Configuring the Client chapter

Summary: related to T12804

Reviewers: ivica

Reviewed By: ivica

Subscribers: miljen, iljazovic

Differential Revision: https://repo.mireo.local/D28182

example/hello_world_over_tcp.cpp

@@ -0,0 +1,31 @@
+//[hello_world_over_tcp
+#include <iostream>
+
+#include <boost/asio/io_context.hpp>
+#include <boost/asio/detached.hpp>
+#include <boost/asio/ip/tcp.hpp>
+
+#include <async_mqtt5.hpp>
+
+int main() {
+	boost::asio::io_context ioc;
+
+	// Construct the Client with ``__TCP_SOCKET__`` as the underlying stream.
+	async_mqtt5::mqtt_client<boost::asio::ip::tcp::socket> client(ioc);
+
+	// 1883 is the default TCP MQTT port.
+	client.brokers("<your-mqtt-broker>", 1883)
+		.async_run(boost::asio::detached);
+
+	client.async_publish<async_mqtt5::qos_e::at_most_once>(
+		"<topic>", "Hello world!",
+		async_mqtt5::retain_e::no, async_mqtt5::publish_props {},
+		[&client](async_mqtt5::error_code ec) {
+			std::cout << ec.message() << std::endl;
+			client.async_disconnect(boost::asio::detached);
+		}
+	);
+
+	ioc.run();
+}
+//]