Add back dark theme fixer or at least a

Remember when it was called “better canvas”? I mean, I do like the new “better campus”. It’s just that lost some of its freedom. Such as fixing the dark theme.

Explanation: Whenever I need to click a specific link on one of my classes on canvas, sometimes my teachers insert their own backgrounds, resulting in my font color going poorly with the background. But I remember there was an option to fix all of that when this extension was first called a better canvas, but now it is gone.