* feat(multi-stream-support) Add screenshare as a second video track to the call.
This feature is behind a sendMultipleVideoStreams config.js flag. sourceNameSignaling flag also needs to enabled. Sending multiple tracks is currently supported only on endpoints running in unified plan mode. However, clients with source-name signaling enabled and running in plan-b can still receive multiple streams .

* squash: check if there is an existing track before adding camera/desktop

* squash: enable multi-stream only on unified plan endpoints.

* feat: Change the screenshare capture fps from UI.
Add the ability to change the capture frame rate for screenshare from the UI. The fps becomes effective only on screen shares that are started after the setting is changed.

* squash: add missing JSDOCs and translations for frames-per-second.

* audio only screen share implementation

* clean up

* handle stop screen share from chrome window

* update icon