feat(rollup-plugin-html): add CSS bundling and minification

[bashmish]

What I did

1. implement bundling and minification via Lightning CSS
2. enable CSS bundling by default since otherwise @import won't be properly working in the output, so I consider this a feature/bugfix
3. do not enable CSS minification by default, in accordance with existing HTML minification rule
4. due to how things are implemented, the output CSS will always be processed by Lightning CSS, resulting in normalization of some CSS properties, therefore tests needed to be updated and this will impact end users too, but that gives consistency in the output, which is a good thing, so I consider this a bugfix
5. added some docs and fixed some old ones

[changeset-bot]

🦋 Changeset detected

Latest commit: 3a9c97b

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@web/rollup-plugin-html	Minor

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[thepassle]

The tests failing is still the same issue we had as before? Maybe we should make a story to fix them as well

Otherwise LGTM