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

Closes team#40354 and team#40382

See merge request tpo/tpa/wiki-replica!18

Looks like /target doesn't actually exist after fabric.

This reverts commit 962ae296.

This is just a guess, I am not actually sure how to handle this.

But hopefully, this will...

Closes: team#40354

We had nothing about the star of the weeks, which was informally
specified. This clarifies that it's responsible for routine tasks, but
also takes care of clarifying the ticket workflow in the gitlab policy.

Closes: #40382

create a new "support" page

See merge request !17

The support page is the go-to page for the "how to get help" question,
which previously was hidden inside the TPA-RFC-2 standard.

This basically copies that part of the TPA-RFC-2 policy, but could
eventually diverge without needing to update the policy, for informal
stuff.

I started working on this page while trying to address
#40382 ("document the triage process"), but I'm not
actually sure triage documentation should go there, as this page feels
more targeted at users, and only users.

howto/incident-response.md would seem like a better space for this.

Also, this is a toplevel page because it's more important than
everything else, so it warrants its own special space.

This is non-normative, so doesn't need discussion.

The bootstrap starts from `/target`, which is unusual in the FHS, but
it's better to live with what's out there than the ideal world.