update link for slack invite

Signed-off-by: Mike Brown <brownwm@us.ibm.com>

README.md

@@ -224,7 +224,8 @@ This will be the best place to discuss design and implementation.
 
 For sync communication we have a community slack with a #containerd channel that everyone is welcome to join and chat about development.
 
-**Slack:** https://join.slack.com/t/dockercommunity/shared_invite/enQtNDM4NjAwNDMyOTUwLWZlMDZmYWRjZjk4Zjc5ZGQ5NWZkOWI1Yjk2NGE3ZWVlYjYxM2VhYjczOWIyZDFhZTE3NTUwZWQzMjhmNGYyZTg
+**Slack:** Catch us in the #containerd and #containerd-dev channels on dockercommunity.slack.com.
+[Click here for an invite to docker community slack.](https://join.slack.com/t/dockercommunity/shared_invite/enQtNDY4MDc1Mzc0MzIwLTgxZDBlMmM4ZGEyNDc1N2FkMzlhODJkYmE1YTVkYjM1MDE3ZjAwZjBkOGFlOTJkZjRmZGYzNjYyY2M3ZTUxYzQ)
 
 ### Reporting security issues