Dark mode

[marcusturewicz]

Dark mode is being added to the editor in #101, but it would be nice to have dark mode more generally throughout the entire site. The theme mode should also be persisted to the browser (e.g. cookie, local storage etc) so it remains when you come back.

This might be a good starting point https://getbootstrap.com/docs/4.1/getting-started/theming/

[marcusturewicz]

This could also be helpful: https://dev.to/ananyaneogi/create-a-dark-light-mode-switch-with-css-variables-34l8

[marcusturewicz]

This looks promising for plug n play: https://github.com/coliff/dark-mode-switch