3.11.x improvements : Admin/Account panels, tables and minor fixes

[TBG-FR]

As said in the title, I highly improved Admin/Account panels look in Dark Theme (sidebars, backgrounds, etc), and did some other minor modifications, especially on tables.

Enjoy ;)

[brunobertoldi]

Admin and Account look great!

[fdellwing]

Admin looks really good 👍

[pbaity]

Looks great! Merging.

[pbaity]

I've mentioned this several times elsewhere, but just to be consistent, a warning that rules that apply to class names like .rcx-css-dlop43 (generated classes) are highly likely to break at the next release (and may already not work for anyone using a different version). Of course we still want the short-term fix, but if there's ever a way to target the same elements via more stable parent or sibling classes, that would be more future-proof.

[fdellwing]

The problem is, that most classes are very general and since RC is full of very specific rules that target generated classes it is hard to get even more specific rules without using the generated classes.

[pbaity]

If there was an emoji on GitHub for "bullseye" I'd react with that instead. I hope in the future that Rocket.Chat will make custom styling easier - it's gotten more difficult over time, not better. Or, of course, they're welcome to introduce a native dark mode anytime now - nothing would make me happier than to retire this repo and declare mission accomplished.