Dark theme for preferences on mac

[adeebahmed]

I don't know too much about how slack structures its css files.

If someone with that knowledge could find the css attributes for the preferences page on mac and style them accordingly, that'd be pretty sweet.

https://github.com/laCour/slack-night-mode/blob/master/css/raw/black.css - is the theme I like in particular 😄

[tplk]

I'm pretty much sure Preferences are the same on other platforms too.
Here's how it currently looks on Windows with gruvbox theme.