removed new UI until its developer returns (he is on hiatus) (or dead)

If that guy isn't dead and we bring back the custom themes, can we make an option to toggle between main content being white or colored in. I loved the evergreen theme but the white page blinds my delicate eyeballs

During the Christmas event my dark mode browser addon was able to do it, but something broke when it turned off and it made everything orange and changing theme didn't do anything