Mention slack channel

Signed-off-by: Ivan Kanakarakis <ivan.kanak@gmail.com>

Author: c00kiemon5ter

contribute.md

@@ -5,8 +5,10 @@ permalink: /contribute/
 ---
 
 The Identity Python consists of a set of inter-related but separate software
-projects sharing common funding and governance. Right now there is a common
-mailing list for discussions about the Identity Python provided by [SUNET](https://sunet.se).
+projects sharing common funding and governance. Right now, there is a common
+mailing list for discussions about the Identity Python provided by [SUNET](https://sunet.se),
+and a [slack channel](https://identity-python.slack.com)
+that you [can join](https://join.slack.com/t/identity-python/shared_invite/enQtNzEyNjU1NDI1MjUyLTM2MWI5ZGNhMTk1ZThiOTIxNWY2OTY1ODVmMWNjMzUzMTYxNTY5MzE5N2RlYjExZTIyM2MwYjBjZGE4MGVlMTM).
 
 Participation in all Identity Python projects is govered by our [Note Well](https://github.com/IdentityPython/Governance/blob/master/Note-Well.md).