Added webmentions and sorted more highlights

Super hyped about switching to Astro. Lots of regressions for now, but v0.0.0.0.0.1 of my highlights system (sort of meant to replace Readwise) is done, and the collections system plus MDX make maintaining the site from my phone way simpler!

I also decided to add Tailwind, and I'm gradually migrating my old styles. Next up... Webmentions and more style/component updates!

Oh, owie, the highlights don’t look so great on mobile :(