update slack link

Author: vroland

README.md

@@ -1,4 +1,4 @@
-[![Documentation Status](https://readthedocs.org/projects/epdiy/badge/?version=latest)](https://epdiy.readthedocs.io/en/latest/?badge=latest) [![Matrix](https://img.shields.io/matrix/epdiy-general:matrix.vroland.de?label=Matrix%20Chat)](https://matrix.to/#/!GUXWriqsBKkWyXzsBK:matrix.vroland.de?via=matrix.vroland.de) [![JoinSlack](https://img.shields.io/badge/Join%20us-on%20Slack-blueviolet.svg)](https://join.slack.com/t/epdiy/shared_invite/zt-uutp3ex1-0CLo_vgVLJJ6BwJNCtPc_g)
+[![Documentation Status](https://readthedocs.org/projects/epdiy/badge/?version=latest)](https://epdiy.readthedocs.io/en/latest/?badge=latest) [![Matrix](https://img.shields.io/matrix/epdiy-general:matrix.vroland.de?label=Matrix%20Chat)](https://matrix.to/#/!GUXWriqsBKkWyXzsBK:matrix.vroland.de?via=matrix.vroland.de) [![JoinSlack](https://img.shields.io/badge/Join%20us-on%20Slack-blueviolet.svg)](https://join.slack.com/t/epdiy/shared_invite/zt-wpl0wm2p-pthLGFm4KAnRAFc4gTVFSg)
 
 EPDiy E-Paper Driver
 =======================================