Feature request: Spectator mode

A channel property to participants enter without emitting audio/video but only watching the others they do.

This could open the possibility to many people assist to a few orators debate or “classroom mode”.

The new property could set different level restriction values:
0 = Only participant mode
1 = Participant mode by default
2 = Spectator mode by default
3 = Only spectator mode but authorised users (my room moderator)

Another improvement will be saving lots of bandwidth and CPU.