feat(website): add autolink headings back

[yanthomasdev]

Summary

This PR adds back the autolink headings that were lost in the Rome -> Biome migration.

Credits to Astro Docs where I respectfully stole this code from 😛

Test Plan

When you hover over a heading, you will now see a new icon that will link to the current heading. This works both in desktop and mobile since the icon will be moved to the most appropriate place according to the viewport.

Notes:

• I added two new small dev dependencies to accomplish this: hastscript & html-escaper.
• This will also apply to blog post entries, where we don't have a table of contents, so that's an extra nicety.
• I've removed some (supposedly) unused code from the astro.config.mjs file - If necessary I can add it back.

Example:

Mobile viewport

Medium-sized viewport (+ hover style example)

Large viewport

[netlify]

✅ Deploy Preview for biomejs ready!

Name	Link
🔨 Latest commit	d556f7b
🔍 Latest deploy log	https://app.netlify.com/sites/biomejs/deploys/657041480d27cf0008428c47
😎 Deploy Preview	https://deploy-preview-1074--biomejs.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 site configuration.

[ematipico]

That's nice! I meant to do it but you anticipated me 😹

[ematipico]

Looks good ! I'll take care of formatting :)