fix: Use css-tree instead of css for parsing /colors

[TheJolman]

the npm package css has a depreciated dependency that's generating a warning on npm install, switching to css-tree resolves the issue as a drop in replacement.

npm warn deprecated source-map-resolve@0.6.0: See https://github.com/lydell/source-map-resolve#deprecated

Also introduced a tbody element on the colors page to silence this warning:

node_invalid_placement_ssr: `<tr>` (src/routes/(site)/colors/color.svelte:12:0) cannot be a child of `<table
>` (src/routes/(site)/colors/+page.svelte:25:4). `<table>` only allows these children: `<caption>`, `<colgro
up>`, `<tbody>`, `<thead>`, `<tfoot>`, `<style>`, `<script>`, `<template>`

This can cause content to shift around as the browser repairs the HTML, and will likely result in a `hydrati
on_mismatch` warning.

Reproducing

First, on main:

rm -r node_modules && npm i

Observe depreciation warning.

Then, on this branch:

rm -r node_modules && npm i

Warning should be gone.

[dianellasy]

LGTM!