Support for detecting unofficial features

[douglaseggleton]

Currently the library does not support the detection of :focus-within https://caniuse.com/#feat=css-focus-within

e.g.

body:focus-within {
  background: green;
}

Thoughts on adding support for this?

[pkuczynski]

I would happily accept a PR if you have some time to work on it?

[clshortfuse]

Fixed:

echo "body:focus-within {}"| npx doiuse --browsers "ie >= 9"
<streaming css input>:1:1: :focus-within CSS pseudo-class not supported by: IE (9,10,11) (css-focus-within)