docs: react native example (#1842)

* feat: add react native example to README.md file

* docs: update TOC of README.md file

README.md

@@ -15,6 +15,7 @@ in JavaScript for node.js and the browser.
 - [Upgrade notes](#notes)
 - [Installation](#install)
 - [Example](#example)
+- [React Native](#react-native)
 - [Import Styles](#example)
 - [Command Line Tools](#cli)
 - [API](#api)
@@ -117,6 +118,13 @@ output:
 Hello mqtt
 ```
 
+<a name="example-react-native"></a>
+
+### React Native
+
+MQTT.js can be used in React Native applications. To use it, see the [React Native example](https://github.com/MaximoLiberata/react-native-mqtt.js-example)
+
+
 If you want to run your own MQTT broker, you can use
 [Mosquitto](http://mosquitto.org) or
 [Aedes-cli](https://github.com/moscajs/aedes-cli), and launch it.