Change slack to discord

Author: defunctzombie

README.md

@@ -86,7 +86,7 @@ You can find examples of different kinds of extensions in the `./examples` direc
 
 ## Stay in touch
 
-Join our [Slack channel](https://foxglove.dev/slack) to ask questions, share
+Join our [Discord](https://discord.com/invite/vUVAdFmMFM) to ask questions, share
 feedback, and stay up to date on what our team is working on.
 
 ## Developer information