Use room tags to categorize rooms into favorites, people, rooms and low priority

Right clicking a room already allows to mark it as favorite or low priority, but this does not actually change anything in the room list currently. The room list needs to show the categories and sort the rooms under them.

Preferably these categories would be collapsible so if you joined a lot of rooms, you can still quickly go to e.g. the low priority rooms by collapsing the categories above.