CI: Added preview links for new-docs

[ugtthis]

• Doc site is built and deployed on Cloudflare Pages similar to new-connect
• Comments a preview link whenever a PR happens
• CLOUDFLARE_PAGES_TOKEN and CLOUDFLARE_ACCOUNT_ID are required.
• Instead of separating build and preview, I put them together into new-docs.yaml
• As seen below, is an example out. I tested out this here to see how it looks.
• Link to PR Preview: https://pr-15.docs-openpilot.pages.dev/
• First step towards new docs.comma.ai #32812

[github-actions]

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