Consider adding CODEOWNERS file for automatically requesting code reviewers

[clepple]

Info: https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners

Could draw from MAINTAINERS, though email addresses would need to be translated to GitHub usernames.

[jimklimov]

On a related note, wondering how many of those entries are up to date... and how to fill in the gaps where an expert is missing but sorely missed?.. Or are there just the "core-maintainers" practically?..

Curiously, was fixing a bug today with collectd builds against current NUT headers, and looked at their CI recipes as an example. They also have the file, so we can look at a practical example https://github.com/collectd/collectd/blob/main/CODEOWNERS :)