Add a CODEOWNERS file

[ydah]

Follow up: https://github.com/rubocop/rubocop-rspec/pull/1762

---

Before submitting the PR make sure the following are checked:

• [x] Feature branch is up-to-date with main (if not - rebase it).
• [x] Squashed related commits together.
• [ ] Added tests.
• [ ] Updated documentation.
• [ ] Added an entry to the CHANGELOG.md if the new code introduces user-observable changes.
• [x] The build (bundle exec rake) passes (be sure to run this locally, since it may produce updated documentation that you will need to commit).

[bquorning]

Actually, I would like to not own this repo (or rubocop-factory_bot), but of course still be part of rubocop-rspec. Is it overkill to make a separate group for each repo?

[ydah]

I don't have a strong opinion. However, it seems to me that creating a team for each repository is a bit difficult to manage.

[pirj]

We have to define a team anyway to use it in codeowners like@rubocop/rubocop-rspec, right?

[pirj]

Thank you!