Warns incorrectly on CSS attribute selector case sensitivity flag

[adamwathan]

Given this CSS:

[type="A" s] {
  color:  black;
}

esbuild warns with:

 > in.css:1:10: warning: Expected "]" but found "s"
    1 │ [type="A" s] {
      ╵           ^

 > in.css:1:11: warning: Unexpected "]"
    1 │ [type="A" s] {

This is actually valid, and is a newer flag similar to the existing i flag which esbuild seems to handle and does not warn about:

https://developer.mozilla.org/en-US/docs/Web/CSS/Attribute_selectors#html_ordered_lists

Thanks so much for your work on this amazing tool, and for Figma! 😍

[evanw]

Huh. It looks like this is some weird Firefox-only syntax. I can add support for this.

[neupauer]

Huh. It looks like this is some weird Firefox-only syntax. I can add support for this.

@evanw Hi, I'm not sure, but this is not a Firefox-only syntax (all browsers except Safari and IE :) support it).

There was a bug in Chrome (Edge, Opera), but it's already resolved see https://bugs.chromium.org/p/chromium/issues/detail?id=1041095

Links:
https://drafts.csswg.org/selectors-4/#attribute-case