feat: versions for docs to support App and Pages router docs

[jacobdubail]

Description of the Change

Adds versioning to Docusaurus to support App Router and Pages Router docs

How to test the Change

cd docs && npm run start to view the changes in the browser.
Pages Router docs are maintained in the docs/versioned_docs/version-pages-router directory.
App Router docs are maintained in the default docs/documentation directory.

Changelog Entry

Added - Pages Router version via npx docusaurus docs:version pages-router
Changed - docusaurus.config.js to include versions and docsVersionDropdown

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added Critical Flows, Test Cases, and/or End-to-End Tests to cover my change.
• All new and existing tests pass.

[changeset-bot]

⚠️ No Changeset found

Latest commit: f16824c

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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Name	Status	Preview	Comments	Updated (UTC)
headstartwp-app-router	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 23, 2025 8:17pm
headstarwp	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 23, 2025 8:17pm

[github-actions]

📦 Next.js Bundle Analysis for @10up/wp-nextjs-app

This analysis was generated by the Next.js Bundle Analysis action. 🤖

🎉 Global Bundle Size Decreased

Page	Size (compressed)
global	83.76 KB (🟢 -42.23 KB)

Details

The global bundle is the javascript bundle that loads alongside every page. It is in its own category because its impact is much higher - an increase to its size means that every page on your website loads slower, and a decrease means every page loads faster.

Any third party scripts you have added directly to your app using the <script> tag are not accounted for in this analysis

If you want further insight into what is behind the changes, give @next/bundle-analyzer a try!

[github-actions]

📦 Next.js Bundle Analysis for @10up/headstartwp

This analysis was generated by the Next.js Bundle Analysis action. 🤖

This PR introduced no changes to the JavaScript bundle! 🙌