[FR] Room topics

[mehtank]

It might be nice to create a longer text "topic" associated with each room, that could be set/updated by the members of that room (e.g. to describe to what will be worked on, what step the room is currently on, etc.; perhaps relevant when deciding which room to star at the start of a session).

• Create an editable topic field next to the title in the room topbar
• Show the topic as a tooltip in the Meeting Rooms sidebar, maybe as a new icon next to people and star
• Maybe turn the icon red when it's changed since entering room (or keep in localStorage?)