[css] Support for SVG 2 CSS Properties

SVG 2 introduces the possibility of setting SVG properties in CSS (see CSS Tricks' post under "Element-specific properties -> "Positioning SVG elements"). This means this example should be valid:

circle {
  r: 2;
  cx: 10;
  cy: 100;
}

path {
  d: 'L0 100';
}

However, these properties trigger the s?css(unknownProperties) warning:

I'm not too familiar with VS Code's insides and what program checks for valid properties. If this belongs somewhere else, I'd be happy to re-issue there.

Thanks! ✨