[RFE]: Create CODEOWNERS entry

[rata]

Current situation

We don't have a CODEOWNERS file in the github repo

Impact

We don't get notified of new PRs except when people Cc us. This is not a big deal, as we don't have lot of PRs now, but it would be nice to get notified

Ideal future situation

Add a CODEOWNERS file, so github assigns us automatically and we get notified.

There might be other alternatives in github, I'm just familiar with this one :)

cc @alban