Feature Request: Display what sessions other players are currently using

[Andreddi]

Is your feature request related to a problem? Please describe.
When using Sliver in multiplayer mode, it's possible to see when a player joins and leaves, but currently there is no way to tell which sessions they are using.

Describe the solution you'd like
When running the "sessions" command, either add a new column that shows the usernames of players using a session, or recolor the sessions that are in use.