addTransceiver
Creates a new RtpTransceiver and adds it to the set of transceivers. Adding a transceiver will cause future calls to CreateOffer to add a media description for the corresponding transceiver.
The initial value of `mid` in the returned transceiver is null. Setting a new session description may change it to a non-null value.
https://w3c.github.io/webrtc-pc/#dom-rtcpeerconnection-addtransceiver
If a MediaStreamTrack is specified then a transceiver will be added with a sender set to transmit the given track. The kind of the transceiver (and sender/receiver) will be derived from the kind of the track.
If MediaType is specified then a transceiver will be added based upon that type. This can be either MEDIA_TYPE_AUDIO or MEDIA_TYPE_VIDEO.
Optionally, an RtpTransceiverInit structure can be specified to configure the transceiver from construction. If not specified, the transceiver will default to having a direction of kSendRecv and not be part of any streams.
Note: These methods are only available with SdpSemantics.UNIFIED_PLAN specified.
Throws
if an error accors in C++ addTransceiver