TAC onboarding follow-ups

[justaugustus]

These are follow-up from the "Open questions" sections:

• Are there additional access requirements not accounted for in this document?
• What are our moderation responsibilities and privileges (GitHub, mailing lists, Zoom)?
• How do we manage rescheduling the TAC meeting to accommodate timezones and/or new member obligations?
• Explicitly, what are the responsibilities of the TAC Chair and Vice Chair? — Simplify docs around Chair election, roles, and responsibilities #432

I'll clean up this list as we move through the items in #426.