[webrtc-pc] Move henbos/webrtc-provisional-stats to w3c/webrtc-provisional-stats (#2379)

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

== Move henbos/webrtc-provisional-stats to w3c/webrtc-provisional-stats ==
As discussed during the [November 2019 Virtual Interim](https://www.youtube.com/watch?v=LxGiXdlOEr0), we should move https://github.com/henbos/webrtc-provisional-stats from my personal github to w3c to reflect the fact that it has been adopted by this working group.

This may include adding a proper introduction, updating some of the config files and making sure the readme and licenses are correct.

Please view or discuss this issue at https://github.com/w3c/webrtc-pc/issues/2379 using your GitHub account