Add link to #git channel on ORNL Slack

README.md

@@ -14,6 +14,8 @@ Folks who are already comfortable with git are strongly encouraged to attend and
 help answer questions, provide tips for new users, and to help advocate for
 expanding the adoption of git at ORNL.
 
+Join us and other ORNL git users on Slack: https://ornl.slack.com/messages/git/
+
 ## Workshop Topics
 Unless stated otherwise, these workshops are held on the following dates at
 9:00am in the JICS Auditorium (Building 5100 Room 128).