Create /doc-locale/ja-jp directory in upstream gitlab-operator project with localized JA content

[DRAFT description, per Scope of upstream / production MRs from the parent epic &104 (closed)\\\]

Goal

Create a merge request in the upstream gitlab-operator project to add the /doc-locale/ja-jp directory with translated Japanese .md content.

This follows the successful implementation in the tech-docs-forked-projects/prod/gitlab-operator forked project: Set up fork-based translation with /doc-locale/... (#125 - closed), and is part of our broader initiative to enable localized documentation across GitLab projects.

Implementation

1. Use the default MR template for the upstream gitlab-operator project: https://gitlab.com/gitlab-org/cloud-native/gitlab-operator/-/blob/master/.gitlab/merge_request_templates/Default.md
2. Add the translated .md file(s) which will create the /doc-locale/ja-jp directory structure in the upstream project
3. Update CODEOWNERS to designate the Localization team as code owners of the newly created directory
4. Verify the structure and run existing CI pipelines to ensure basic functionality [this needs more specifics, to be developed in MVC 1 - CI Testing for /doc-locale/ja-jp/ (#127 - closed)\] 🔖
5. Follow upstream projects' code review requirements (Code Review Guidelines in GitLab Docs)
6. Identify and communicate with maintainers who will be reviewing changes and performing the final merge (Engineering Projects list of maintainers in GitLab Handbook)
7. ...

Testing

1. Leverage existing CI tests that run on docs content [this needs more specifics] 🔖
2. Nuances of Japanese content validation will be addressed in separate CI test development work [likely in MVC 1 - CI Testing for /doc-locale/ja-jp/ (#127 - closed)
3. ...
4. ...