Artur Pietkiewicz (apieti), I have done a first pass at dark mode. You can enable it using the dropdown next to your username in the top-right of the site (see pic).

It's using an automated library to do the switch, so not everything is perfect. There are a couple of known issues on the match page, but everything should be readable.

When I get a chance I'll do a bit more cleanup. I can't see immediately how to fix these minor issues.

I was suggesting a "pick a colour for background" as well.

I would choose dark grey. Both black and grey (but especially black) saves some (more) battery if you are accessing the website from phone.