[Desktop] Add tab support (eg. like Notion desktop)

I want to be able to cross-reference different parts of a community easily.

Example use-cases

• work in a course > question pops-up > open new tab with course discussion to drop the message.

• doing stuff in community A > wanting to apply/share in community B > open new tab with community B to do the thing.

Things like that.

PS - Maybe add a Desktop app Category here in the request board.