chore(site): LightningCSS (#8929)

* use lighteningcss

* Update sites/svelte.dev/package.json

Co-authored-by: Ben McCann <322311+benmccann@users.noreply.github.com>

* Update vite

* use browserlist

---------

Co-authored-by: Ben McCann <322311+benmccann@users.noreply.github.com>

Author: PuruVJ