Team around kevinvenalainen/allow create encoded streams

[ibc]

NOTE: No idea how I ended creating yet another branch. In theory I was pushing to PR #300...

Fixes #299

Allows calling clients to add sender and receiver callback functions which are executed synchronously after RTCRTPSender/Receiver creation. This feature is targeted to Chromium browsers and allows applications to call createEncodedStreams() in the callback functions in order to create WebRTC Encoded Transforms.

Example Usage

const consumer = await recvTransport.consume({
  xxxxx,
  xxxxx,
  onRtpReceiver: (receiver) => {
    const { readable, writable } = receiver.createEncodedStreams();
    readable.pipeTo(writable);
  }
});