Update Slack Community link

Repo README has stale Slack community link. Kindly update it. I would love to join.

https://join.slack.com/t/bomworkingcommunity/shared_invite/zt-26mocokw4-NkZfF2kevpmZjzkZh5bDxg gives me following error:

> Your invitation has been revoked. Please contact your workspace owner and ask them to resend it.