[css-cascade] New syntax for making an entire layer important

I have some user styles (Stylus extension) that I’m enforcing on a website. For example:

.sticky-header {
  position: static !important;
}

.video-popup {
  display: none !important;
}

Instead of writing !important in every declaration, I would prefer if I could just put my styles inside an important layer:

@layer stylus-extension !important {
  .sticky-header 
     position: static;
  }

  .video-popup {
    display: none;
  }
}

The longer the user styles are, the worse the !important repetition becomes. This repetition could be avoided with a new syntax.

Start by reviewing the proposed @layer syntax and the existing CSS cascade layer rules referenced by the issue. Check the six-comment thread for prior discussion before determining whether the proposal has a settled direction. Done means an agreed syntax and corresponding CSSWG specification update, rather than an implementation patch.