docs: add notice about source code move (#258)

Author: derberg

README.md

@@ -1,3 +1,12 @@
+# We've Moved! 🚚
+The code for this repo is now a part the AsyncAPI Generator monorepo: https://github.com/asyncapi/generator/tree/master/apps/react-sdk
+
+Please file bugs and feature requests as issues on the AsyncAPI Generator repo: https://github.com/asyncapi/generator/issues
+
+The package name did not change and is still available in npm as: https://www.npmjs.com/package/@asyncapi/generator-react-sdk
+
+---
+
 [![AsyncAPI React SDK](./assets/readme-banner.png)](https://www.asyncapi.com)
 <!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
 [![All Contributors](https://img.shields.io/badge/all_contributors-1-orange.svg?style=flat-square)](#contributors-)
@@ -130,4 +139,4 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
 
 <!-- ALL-CONTRIBUTORS-LIST:END -->
 
-This project follows the [all-contributors](https://github.com/all-contributors/all-contributors) specification. Contributions of any kind welcome!
+This project follows the [all-contributors](https://github.com/all-contributors/all-contributors) specification. Contributions of any kind welcome!