I can't get this to work though. I'm not sure what I'm doing wrong. I get a few issues:

#1 error 1 : 1 Unexpected "GM_addStyle(". error 1 : 13 Unexpected "". error 13 : 1 Unexpected "". error 13 : 2 Unexpected ")". error 13 : 3 Unexpected ";".

Edit: turns out OPs code works perfectly and the ones from below just straight up don't work for me.

https://chrome.google.com/webstore/detail/stylus/clngdbkpkpeebahjckkjfobafhncgmne

This is the chrome link