Add CODEOWNERS

[mmagician]

Description

closes: #XXXX

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (master)
• Linked to Github issue with discussion and accepted design OR have an explanation in the PR that describes this work.
• Wrote unit tests
• Updated relevant documentation in the code
• Added a relevant changelog entry to the Pending section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

[weikengchen]

There is an error that prevents the PR from being merged: lint private_in_public has been removed: replaced with another group of lints, see RFC https://rust-lang.github.io/rfcs/2145-type-privacy.html for more information

I replaced it with the guidelines given in the RFC, will see how it works...

[weikengchen]

Ok, it seems alternatives are not stable yet, so the best bet is to remove this lint for now.