Merge pull request #9549 from jtpio/binder-readme

Update the Binder link in the README to point to a 3.0 Binder

README.md

@@ -17,7 +17,7 @@
 [![Discourse](https://img.shields.io/badge/help_forum-discourse-blue.svg)](https://discourse.jupyter.org/c/jupyterlab)
 [![Gitter](https://img.shields.io/badge/social_chat-gitter-blue.svg)](https://gitter.im/jupyterlab/jupyterlab)
 
-[![Binder](https://mybinder.org/badge_logo.svg)](https://mybinder.org/v2/gh/jupyterlab/jupyterlab-demo/master?urlpath=lab/tree/demo)
+[![Binder](https://mybinder.org/badge_logo.svg)](https://mybinder.org/v2/gh/jupyterlab/jupyterlab-demo/3818244?urlpath=lab/tree/demo)
 
 An extensible environment for interactive and reproducible computing, based on the
 Jupyter Notebook and Architecture. [Currently ready for users.](https://blog.jupyter.org/jupyterlab-is-ready-for-users-5a6f039b8906)