dataChannelOnly option

[saba-abi]

Component your feature request relates to

• Signalling server
• Frontend library
• Frontend UI library
• Matchmaker
• SFU
• This repo

Problem your feature solves? Please describe.
We have a use case in our custom implementation where we use a data-channel-only connection without a media stream for a control-only UI, reducing data usage when media is not needed.

Is it possible to add support for this in the official frontend library as well? We are currently migrating to the official libraries.

Describe the solution you'd like
Boolean flags that control:

• offerToReceiveAudio
• offerToReceiveVideo

or dataChannelOnly that controls both.