Support Rust-lang Zulip Archive

[Nemo157]

Especially since it is currently unstyled, it would be great to have ayu styling here: https://zulip-archive.rust-lang.org/

[Nemo157]

I ended up writing a little userstyle for it: https://gist.github.com/Nemo157/b30e9687927117836b09773f73e7e1cc, I might get around to opening a PR for it at some point, otherwise I hereby declare that it's under MIT license if someone else feels like integrating it.

[Cldfire]

I'm more than happy to accept a PR if you get around to it! 😄