(themes) "faded" comments should be optional, not default.

I think perhaps for accessibility that a pass over ALL the `comment` styles in **all** (1st party, not Base16) themes and pulling them up to a `3` or `4.5` contrast and then recommend that those who want the common "i can barely see the comments" look/feel should apply `opacity` of their desired choosing to `hljs-comment`. That way we equally support both accessibility and user choice.

I'm going to split this into a separate issue and add it to the v12 list.

**Update: Definitely seems like we should first update the theme checker tool to use APCA.**

_Originally posted by @joshgoebel in https://github.com/highlightjs/highlight.js/issues/3482#issuecomment-1040565915_