Youenn as co-editor of Media Capture and Streams

Hi again,

Youenn Fablet has agreed to be listed as co-editor of Media Capture and
Streams
https://w3c.github.io/mediacapture-main/

The chairs and staff feel this is long overdue, due to Youenn's existing
contributions to this spec, both in the form of PRs, and regular attendance
at many Editor's Meetings for quite some time.

Cheers!

Jan-Ivar, for the chairs