Update README.md

Add slack channel badge

Author: leandrosimoes

README.md

@@ -5,6 +5,7 @@ React Native Android Notification Listener is a library that allows you to liste
 [![Codacy Badge](https://api.codacy.com/project/badge/Grade/bfbf75b8e92f446481f5ce4b0d077b0b)](https://app.codacy.com/manual/leandrosimoes/react-native-android-notification-listener?utm_source=github.com\&utm_medium=referral\&utm_content=leandrosimoes/react-native-android-notification-listener\&utm_campaign=Badge_Grade_Dashboard)
 [![npm version](https://badge.fury.io/js/react-native-android-notification-listener.svg)](https://badge.fury.io/js/react-native-android-notification-listener)
 ![Node.js Package](https://github.com/leandrosimoes/react-native-android-notification-listener/workflows/Node%2Ejs%20Package/badge.svg)
+[<img src="https://img.shields.io/badge/slack-@lesimoes/help-blue.svg?logo=slack">](https://lesimoes.slack.com/messages/C04JV5CRGJH) 
 
 ## Installation