[Proposal] Expand inline style='' attributes to allow pseudo-class/element styling

style-attr
selectors
Tags: #<Tag:0x00007f8e4858c8d8> #<Tag:0x00007f8e4858c798>

#21

What about style-rules. If we borrow the &-syntax from preprocessors we would get this:

<div css-rules="
  & {
    color: red;
  }
  &:hover:active::before {
    content: 'You are clicking: ';
  }
  .is-editing &::after {
    content: ' (editing)';
  }
">Hello world</div>

div.cssRules.inserRule(`
  & {
    opacity: 1;
  }
`)

div.cssRules.inserRule(`
  .nav-open & {
    opacity: 1;
  }
`)

Or simply setAttribute css-rules.

This would make every element with the attribute a styleaheet. & would naturally have element-specificity.

We could also borrow :self from the stage-1 element queries spec for consistency.