Add specific team members to codeowners who can approve MRs

I know we have several people that are contributing here, but I feel bad asking for reviews from random team members that haven't explicitly stated they want to do reviews.

So I think we should find volunteers who can maintain this repository and also agree to be added as maintainers.

The tests here are very thorough, so I don't think a super high level of rust expertise is necessary, which should make the pool of potential maintainers a bit bigger.

Note I've edited the description of this issue after considering alternatives to the original request.