Indicate which users are more active in the channel

[spoulson]

In order to show who in the room has been more actively participating in the channel, indicate which users are idling and which have recently chatted.

This indication can be a star or similar icon for recently active, such as within the last 2 minutes. For users who haven't chatted in over 5 minutes, sort them to the bottom of the user list with an icon indicating they are idle.

Update these indicators as chat messages arrive. Update idle indicators every minute.