Feat: Create control-panel for settings

[malmen237]

          During the original project we discussed creating something like a "Admin Panel" for a call, where an admin-type user (or anyone) could go to change the settings for everyone in the call, things like:

• mute / unmute user (for everyone)
• change user volume by updating their local input volume (for everyone, using custom message + Audio Context GainNode)
• kick user

I kind of like the idea of having settings like these on a separate panel, so that the buttons are not immediately accessible to everyone

Originally posted by @martinstark in #265 (comment)