Owners file to specify reviewers

Maybe this is only interesting when you're using mono-repo's.

See the auditing part of https://secure.phabricator.com/book/phabricator/article/owners/ and https://www.chromium.org/developers/owners-files

/cc @markpundsack @JobV @regisF

Edited by 🤖 GitLab Bot 🤖