Add missing pseudo elements

[CroModder]

Hi all, is there a reason why some pseudo element selectors are not included in this list?
At first I thought that e.g. ::-webkit-progress-bar is not included in there because it's an non standard feature but then I found out that also other non standard pseudo elements are already included in that list.
I would be happy to open PR if you want to support other non standard pseudo elements if you decide for that.

[askoufis]

::-webkit-progress-bar is present in that list, but ultimately it's a hard-coded list that hasn't been updated in a while, so I'm not surprised that there are some missing pseudo-selectors that have been added to CSS in recent years. A PR would be welcome 😃.

[CroModder]

I meant to say meter-bar is missing, but went on mdn and copied wrong selector 😄
Ok, great, will prepare a PR in upcoming days

[askoufis]

Addressed in #1207