Fix selector-pseudo-element-no-unknown false positives for ::highlight

[jathak]

What steps are needed to reproduce the bug?

Code like

::highlight(a) {
  background-color: green;
}

What Stylelint configuration is needed to reproduce the bug?

{
  "rules": {
    "selector-pseudo-element-no-unknown": true
  }
}

How did you run Stylelint?

Online Demo

Which version of Stylelint are you using?

14.12.1

What did you expect to happen?

No problems to be reported.

What actually happened?

The following problem was reported:

1:1-12    Unexpected unknown pseudo-element selector "::highlight" (selector-pseudo-element-no-unknown)

This pseudo-element is part of the CSS Custom Highlight API and was shipped in Chrome 105.

Does the bug relate to non-standard syntax?

No response

Proposal to fix the bug

PR incoming

[ybiquitous]

@jathak Thanks for providing the precise reproduction. I've copied and pasted an "Online Demo" link in this issue description. Also, thank you for creating a quick-fix PR. I'll soon review it.