Add Harbor registry development page to global navigation

What does this MR do and why?

A development doc was added in gitlab!107902 (merged), but never given a global navigation entry.

CC @aqualls @zhzhang93

Screenshots, screen recordings, or links to review app

• Before: https://docs.gitlab.com/ee/development/packages/harbor_registry_development.html
• After: https://eread-add-habor-registry-development-page-to-global-nav.docs.gitlab-review.app/ee/development/packages/harbor_registry_development.html

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Configure a local GitLab Docs environment: https://gitlab.com/gitlab-org/gitlab-docs/-/blob/main/doc/setup.md.
2. Check out branch from this MR.
3. Run make view and check the page.

Merge request acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this merge request.