Set code owners for packaging files
It's useful for the packaging team to be CC'ed on PRs that change files to packaging so we can review if we need to change anything. Github introduced code owners which can help us with this. See https://github.com/blog/2392-introducing-code-owners for more information.
Fixes #21603 - Add code owners
This is an experiment to implement github code owners1. The idea is
that the packaging team will be added to any changes to dependencies.
This should allow us to make the packaging changes needed keeping