[Docs site] refactor: switch to tabs

[Cherry]

This PR closes #5260. See that issue for more information as to the "why".

This PR also fixes A LOT of code samples (JS, TS, HTML, etc.) that were syntactically invalid. There were a lot, which are now caught with prettier. 😅

This is a very large PR and will get out of sync really quickly, so if someone else would rather take up this work, let me know.

Preview: https://chore-tabs.cloudflare-docs-57q.pages.dev/. I've done a precursory look around and couldn't find anything broken, but I haven't checked every single page. It's unlikely tabs will break anything, but there is a small chance.

[Cherry]

I'm very happy to rebase this whenever someone is ready to merge, please just let me know. Or close it entirely if someone else would prefer to handle.

[Cherry]

I'm going to close this since it's been untouched for months. If anyone is interested in working on this in the future, please let me know.