Create Japanese documentation directory

What does this MR do and why?

Adding Japanese Documentation Structure

This MR adds a Japanese translated documentation file within a new /doc-locale/ja-jp/ directory structure, which will enable http://docs.gitlab.com/ja-jp/. We're starting with a single translated file to establish the directory structure, with more translations to follow.

Important Notes

1. The docs Hugo project is not currently configured to consume content from the /doc-locale/ directory. When it is, we will iterate on the DOCS_LOCALIZATION_PIPELINE to build the docs in the same way the DOCS_PIPELINE does.
2. We are simply verifying the file is properly linted

Related Changes

This Charts MR has sister counterparts across GitLab projects that comprise our documentation site (GitLab, Operator, Charts, & Runner). A change to the docs site will follow to launch docs.gitlab.com/ja-jp/ that will use content from the /doc-locale/ja-jp/ directory.

Please see the SSOT issue for all information related to creating the /doc-locale/ directory structure to launch the Japanese documentation site.

Specific Changes of this MR

1. Adds a single Japanese translated file to /doc-locale/ja-jp/
2. Updates CODEOWNERS to designate @gitlab-com/localization/maintainers as owners of the new /doc-locale directory

Note: We also need to make some validation checks to add localization specific jobs. To tackle multiple unknown failures, the following sections will be delivered in a separate MR (adding them here as a reference only):

1. Creates a new DOCS_LOCALIZATION_PIPELINE rule that is triggered when a branch name is prepended with docs-i18n or comes from https://gitlab.com/gitlab-com/localization/tech-docs-forked-projects/prod/omnibus-gitlab.
2. Creates i18n-specific CI jobs that mirror existing doc CI to lint content:
   • docs-lint-i18n content
   • docs-lint-i18n markdown

References

1. https://gitlab.com/gitlab-com/localization/docs-site-localization/-/issues/102 -> Primary issue with all context related to this work.
2. gitlab-com/localization&104 (closed) -> primary epic with more context for all the relevant issues
3. https://gitlab.com/gitlab-com/localization/docs-site-localization/-/issues/119 -> Engineering issue for this MR.

How to set up and validate locally

There's currently no markdown linting validation for this particular MR, so technically there's no direct way to validate the changes. However, once we add the validation linting in this issue, we should be able to use the following steps in to validating.

docs-lint-i18n markdown Test markdown linting for localized content

1. Make edits to /doc-locale/ja-jp/installation/_index.md that will fail the markdown linter.
   • For example: remove spaces around lists, use inconsistent heading styles, or add improper indentation
2. Run the linter locally to verify it catches the issues:
   • markdownlint-cli2 'doc-locale/**/*.md'

docs-lint-i18n content Test content linting for localized files

1. Make edits to the Japanese file that will fail Vale rules.
   • For example: remove the frontmatter title key, add corporate jargon, or use passive voice
2. Run Vale locally to see the validation errors:
   • vale --minAlertLevel error doc-locale

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.