Add Translation MR Review Workflow to localization handbook
Summary
Adds the Translation MR Review Workflow page to the localization team handbook section. This content was previously maintained in the Docs Site Localization project and is now being brought into the handbook for better discoverability.
What's included
The page defines the assignee and reviewer roles, draft status, and review process for translation merge requests, covering:
- Tech Docs (Upstream): Two-round review process (fork + upstream) with detailed assignee and reviewer responsibilities
- Marketing Site: Simplified review process with Draft mode defaults and flexible approval rules
New file
content/handbook/marketing/localization/translation_mr_review_workflow.md
The page will be available at: https://handbook.gitlab.com/handbook/marketing/localization/translation_mr_review_workflow/