[Umbrella Issue] Re-document communication methods on the website

[celestehorgan]

• [x] Add a page to website for workstreams
• [x] Add/link? public calendar from website
• [x] Add link to Slack inviter
• [x] Document workstream mailing lists somehow

I'm sure there's things I'm missing cc: @justaugustus, @edwarnicke  – any other thoughts?

[gkarthiks]

@celestehorgan the slack inviter is added already right? https://communityinviter.com/apps/inclusive-naming/invite