Add moz.yaml and update `update.sh` to match other media libraries.
Note after upstream's switch from SVN to git the RSC headers have changed,
however, these changes have not yet been committed. I've updated the patch
that had hunks with context extending into the RSC header so it continues to
apply after pulling from git.
Differential Revision: https://phabricator.services.mozilla.com/D11975
--HG--
extra : moz-landing-system : lando