Update README.md [skip ci]

Author: hoc081098

packages/rxdart/README.md

@@ -4,6 +4,10 @@
 <a href="https://flutter.dev/docs/development/packages-and-plugins/favorites"><img src="https://docs.flutter.dev/assets/images/docs/development/packages-and-plugins/FlutterFavoriteLogo.png" width="100" alt="build"></a>
 </p>
 
+<p align="center">
+<img src="https://github.com/ReactiveX/rxdart/blob/master/packages/rxdart/screenshots/logo.png?raw=true" height="200" alt="RxDart" />
+</p>
+
 [![Build Status](https://github.com/ReactiveX/rxdart/workflows/Dart%20CI/badge.svg)](https://github.com/ReactiveX/rxdart/actions)
 [![codecov](https://codecov.io/gh/ReactiveX/rxdart/branch/master/graph/badge.svg)](https://codecov.io/gh/ReactiveX/rxdart)
 [![Pub](https://img.shields.io/pub/v/rxdart.svg)](https://pub.dartlang.org/packages/rxdart)