The output format for this was confusing. When "FAIL" becomes "PASS" the
natural assumption is that's good. So, make it always output pass for
correct results, and fail for incorrect. Also, replace the
supposed-to-fail pseudo-element name with one that will never be
supported, instead of a webkit one that we did end up adding support
for! 😅
Added a couple of env() cases which will pass with the following commit.
A couple of fixes here:
- Parse a `<complex-selector>` instead of a `<selector-list>`
- Don't match if any unknown `::-webkit-*` pseudo-elements are found
