Feat/create metadata impl

[HelloItsJustin]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes Last updated: feeding data through front matter, new "created" metadata #5691) and the maintainers have approved on my working plan.

Closes #5691.

This PR adds creation metadata support for docs, mirroring the existing last_update metadata flow. Docs can now expose when a page was originally created and who created it, using front matter values first and VCS metadata as a fallback.

The new behavior is opt-in and disabled by default, so existing sites keep the same behavior unless they enable the new plugin options.

This PR adds:

• showCreateTime and showCreateAuthor docs plugin options, both defaulting to false
• New front matter fields: last_update_time, last_update_author, create_time, and create_author
• Front matter validation for the new fields
• Creation metadata resolution from front matter first, then VCS history
• createdAt and createdBy fields in docs metadata
• Classic theme footer rendering for creation metadata
• Theme translation message IDs for the new footer text
• Documentation for the new options and front matter fields

Test Plan

Validated locally with:

pnpm test packages/docusaurus-plugin-content-docs
pnpm test packages/docusaurus-theme-classic
pnpm test packages/docusaurus-utils/src/__tests__/lastUpdateUtils.test.ts
pnpm build

Results:

• Docs plugin tests passed: 380 tests
• Classic theme tests passed: 65 tests
• Focused utility metadata tests passed: 21 tests
• Full package and website build passed

Local validation notes:

• pnpm lint currently fails because the existing root script calls lint:SPELLING, while the script is named lint:spelling.
• pnpm lint:ci passes eslint, stylelint, and cspell, then fails on existing syncpack lint dependency policy issues unrelated to this PR.
• Full pnpm test fails locally in unchanged Windows-sensitive VCS/submodule tests, not in the docs metadata tests changed by this PR

Relevant documentation page:

• /docs/api/plugins/plugin-content-docs

Related issues/PRs

Closes #5691.

[netlify]

✅ [V2]

Built without sensitive environment variables

Name	Link
🔨 Latest commit	441e563
🔍 Latest deploy log	https://app.netlify.com/projects/docusaurus-2/deploys/6a2d726c973cba000818639c
😎 Deploy Preview	https://deploy-preview-12166--docusaurus-2.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.