Improve docs of @supports on CSSGroupingRules

[etc-tiago]

I'm trying to correct the issue #19 through a pull request and the following block that code caught my attention:

export interface CSSGroupingRules<
  P extends Record<string, any> = CSSProperties
> {
  '@media'?: {
    [conditionText: string]: CSSRules<P>;
  };
  '@supports'?: {
    [conditionText: string]: CSSRules<P>;
  };
}

source: src/cssTypes.ts

What does @supports do? I couldn't find it anywhere else in the code.

[TxHawks]

@supports is a css at-rule, which, much like @media, is nestable. It is used for built-in feature detection

[etc-tiago]

@TxHawks Thanks for clarification