Add feature for CSS mixins (@mixin, @contents, and @apply) #3465
Description
Specification
- https://drafts.csswg.org/css-mixins/#defining-mixins
- https://drafts.csswg.org/css-mixins/#using-mixins
Description
(I don't really know this feature well, I'm spitballing here based on skimming the spec.)
The @mixin and @contents at-rules define a reusable block of styles that can be varied by arguments. The @apply at-rule calls the mixin inserts its result at the call site.
Documentation
Discovered via #3399 and WPT.
https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_custom_functions_and_mixins
Browser support
None, AFAICT.