TPA-RFC-12: add triage and office hours to TPA-RFC-2

This is a patch that should be merged once TPA-RFC-12 is adopted: https://gitlab.torproject.org/tpo/tpa/team/-/wikis/policy/tpa-rfc-12-triage-and-office-hours

This should close team#40382 (closed) and team#40354 (closed)