[webrtc-pc] "Create an RTP sender" doesn't handle creating from SDP (#2072)

alvestrand has just created a new issue for https://github.com/w3c/webrtc-pc:

== "Create an RTP sender" doesn't handle creating from SDP ==
The section on applying a remote description says:

If no suitable transceiver is found (transceiver is unset), run the following steps:
- Create an RTCRtpSender, sender, from the media description.

The link to "Create an RTCRtpSender" goes to:

To create an RTCRtpSender with a MediaStreamTrack, track, a string, kind, a list of MediaStream objects, streams, and optionally a list of RTCRtpEncodingParameters objects, sendEncodings, run the following steps:

It's not obvious how to construct the parameter list to this algorithm from the media description.
(In particular I was looking for a place to attach the description of how one constructs a list of RTCRtpEncodingParameters from the SDP description. I think I know what to write, but it's not obvious where to attach it.)

Please view or discuss this issue at https://github.com/w3c/webrtc-pc/issues/2072 using your GitHub account