Show unread count in room list

[VAWVAW]

• Differentiate unread rooms between mention, notification (unmuted message), and unreads (muted message).
• Show the number of unreads in the room list (mentions + notifications for unmuted rooms and unreads for muted rooms)
• Only mark mention and notification rooms as bold in the room list.
• Allow sorting the room list by mention or notification.

This is based on discussion in #iamb-users