Color design

The current color scheme is good, but a little low-contrast. The high-contrast theme fixes this, but it could also probably be better.

Also, dark mode would be really awesome. I think there's a significant amount of CSS to fix this, though.

dark-mode is done thanks to @mdlu!

The GCal export button should also change colors in dark mode. There is a dark mode version of the button (although you have to edit Google-provided files in some weird program)- I probably should've made one back when I made the button. I'll add links to this sometime.