Add missing slack invite link (#26)

Signed-off-by: Kevin Roche <[email protected]>

Author: KPRoche

docs/community/contact_us.md

@@ -7,7 +7,10 @@ sidebar_position: 1
 There are several ways you can join the community effort to develop and enhance llm-d
 
 - Via the [**Github pages for llm-d:** https://github.com/llm-d](https://github.com/llm-d)**
-- Via our [**Slack Workspace:** https://llm-d.slack.com](https://llm-d.slack.com)
+
+- Via our [**Slack Workspace:** https://llm-d.slack.com](https://llm-d.slack.com) 
+    Inviter link to [**join the Slack workspace**](https://inviter.co/llm-d-slack)
+
 - Via [**Reddit**: https://www.reddit.com/r/llm_d/](https://www.reddit.com/r/llm_d/)
 - We host a weekly standup for contributors on Wednesdays at 1230pm ET. Please join: [Meeting Details](https://calendar.google.com/calendar/event?action=TEMPLATE&tmeid=NG9yZ3AyYTN0N3VlaW01b21xbWV2c21uNjRfMjAyNTA1MjhUMTYzMDAwWiByb2JzaGF3QHJlZGhhdC5jb20&tmsrc=robshaw%40redhat.com&scp=ALL)
 - We use Google Groups to share architecture diagrams and other content. Please join: [Google Group](https://groups.google.com/g/llm-d-contributors)