Update for Sassy dark mode https://no-pe.netlify.app/dark-mode/
Now with #DartSass.
Short version: I want light/dark themes that are backwards compatible. With Dart Sass, we create two maps, one for light and one for dark colors. Then, we use them in a `mixin` for all our color information. Finally, we include it twice: once as the default and once behind the media query.