Ability to mark as "away" and use it for the maintainer filter in package search

[polyzen]

Add an "away" checkbox to https://archlinux.org/devel/profile/ that one could use when they go on vacation and such.
We could then, eg., easily filter for packages that have a maintainer that's away and is flagged out-of-date, and give them a hand.

Considerations:

• Only for packages that have all packagers away?
• Require being logged-in in order to filter by away?

Don't know if this is feasible, but it would be nice to have.