Update codeowners to allow for self edits of privacy

1. Change Summary

This MR makes three related changes to the privacy pages and their CMS configuration:

CODEOWNERS

• Added /content/en-us/privacy/ to CODEOWNERS to scope approval requirements for privacy content edits.

Privacy template (app/components/templates/Privacy.vue)

• Added a new Privacy page template supporting a side navigation panel, an optional intro section above the nav, and the main markdown content body.
• Navigation links are defined explicitly in the page YAML (rather than auto-inferred from headings), giving content editors full control.
• Uses overflow-y: auto on the side nav so a scrollbar only appears when content actually overflows.

Privacy content files

• Migrated all three privacy pages (Privacy Statement, Cookie Policy, U.S. State Privacy Rights) to a structured content: { intro, content, nav } YAML schema.
• Each page now has an explicit nav list defining the side navigation links and their anchor IDs.
• The Privacy Statement (index.yml) has no intro section; the other two pages use the intro for their preamble content.

Decap CMS (public/admin/pages/)

• Added a new Pages CMS dashboard at /admin/pages/ with a files-based collection covering all three privacy pages.
• All three pages share the same contentWithIntroFields schema in the CMS config, which includes intro (optional markdown), content (markdown), and nav (list of { text, id } items).

2. Testing Steps

Page	URL
Privacy Statement	https://update-codeowners-privacy.about.gitlab-review.app/privacy/
Cookie Policy	https://update-codeowners-privacy.about.gitlab-review.app/privacy/cookies/
U.S. State Privacy Rights	https://update-codeowners-privacy.about.gitlab-review.app/privacy/us-state-privacy-rights-and-disclosures/
Pages CMS dashboard	https://update-codeowners-privacy.about.gitlab-review.app/admin/pages/

1. Visit each privacy page and confirm the side navigation renders correctly with the expected links
2. Click each nav link and confirm it scrolls to the correct section
3. On the Cookie Policy and U.S. State pages, confirm the intro section renders above the side nav
4. On the Privacy Statement page, confirm there is no intro section and the content renders directly
5. On a short privacy page, confirm the side nav does not show an unnecessary scrollbar (verifying overflow-y: auto)
6. Visit /admin/pages/ and confirm all three privacy pages are editable via the CMS, with Intro, Content, and Navigation fields visible. See the Decap local development guide for steps on running the CMS locally.