Support @scope rule

[yisibl]

Describe the feature

Chrome 118 is shipping soon, which is expected to be one of the more popular CSS features, giving new hope for style isolation of components.

• Explainer https://css.oddbird.net/scope/explainer
• Specification https://drafts.csswg.org/css-cascade-6/#scope-atrule

Example:

<style>
  @scope (.foo) to (.limit) {
    .green { background-color: green; }
  }
</style>

<div class=foo>
  <div class=green>Green</div>
  <div class=limit>
      <div class=green>Not green (within .foo, but below .limit)</div>
  </div>
</div>

<div class=green>Not green (not within .foo)</div>

Authors can also automatically scope the styles to <style>’s parent element by dropping the selector(s) in @scope’s prelude:

<div>
  <style>
    @scope {
      .green { background-color: green; }
    }
  </style>
  <div class=green>Green</div>
</div>

<div class=green>Not green</div>