Support "dark mode" theme

[mcrumm]

I am sure to be simplifying a bit, but I would like to explore adding a config option for dark_mode that is a boolean and we load a CSS file that is so named.

Edit: Adjusted for dark mode discussion

[mcrumm]

// @archdragon

[josevalim]

I am not a big fan of this approach because we have a non-reasonable amount of custom CSS, so what happens? Is this custom CSS meant to work with all possible themes? And then even if someone were to reimplement all of the CSS in a custom theme, what happens when we do a new version, where we add/change/remove classes? So to me this is all a bit too coupled for us to allow any theme to be plugged in.

[mcrumm]

I will be honest– I made a naive assumption that things were mostly built-in.

I agree on all points. If the theme is not easily swappable then there is little benefit, and backwards compatibility is a real concern.

I am happy to close this as-is, but I wonder if any amount of "customization" is possible. For instance, would we accept a PR to support a "dark mode"?

[josevalim]

We should accept a PR for a dark mode, yeah. :)