Support audio only calls

[rockneverdies55]

Support for audio only (without video) calls would be nice to have feature...

When/If you add the feature...
Please put a separate button for audio calls. Closing the camera after making a video call is annoying...

[graywolf336]

👍

[Sing-Li]

👍

On native mobile apps, it would be ideal to hook into the contact list so you can Rocket.Chat 'call' a contact directly.

[Sing-Li]

Implemented on #989. Closing this ticket.