Support for :is and :where selectors inside style.

[minht11]

Could support be added for :is selector, so use case like this would work:

style({
  background: 'red',
  selectors: {
    '&:is(:focus-within, :hover)': {
      background: 'blue',
    }
  }
})

There probably would be some restrictions to it, but since :is selector references element itself it shouldn't be too much of a problem.
You can use globalStyle as an alternative right now, but it doesn't feel as clean.

[mattcompiles]

This was resolved in #204