Add "Trash" feature for Docs Sites

[outwebbed]

Recently I inadvertently deleted a docs site, and unfortunately there is no way to undo this (as opposed to Spaces where you get 7 days to recover from the trash.) This would be a helpful feature for accidental deletions of doc sites.

[emmerich]

hey @outwebbed I think we'll build this eventually, sounds like a good safety net. I don't have an ETA for you but it's being tracked internally.

In the meantime we're shipping a change where a site must be unpublished before it can be deleted. Hopefully this helps catch any mistaken deletions until we implement the full "trash" feature.