Add code owner rules for JH

What does this MR do and why?

Related issue: https://gitlab.com/gitlab-jh/gitlab-jh-enablement/-/issues/213 @daveliu

Add code owner rules for JiHu GitLab.

WHY

FILE_NAME = 'CODEOWNERS'
FILE_PATHS = [FILE_NAME, "docs/#{FILE_NAME}", ".gitlab/#{FILE_NAME}"].freeze

The codeowner function will search for the first existing file in order from the above three files.

JH can not adjust the rules in JH repo without changing the codeowner function.

All new rules are limited to the jh directory, so it will not affect Upstream.

Screenshots or screen recordings

How to set up and validate locally

MR acceptance checklist

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