Separete theme color for dark mode

[bartekpacia]

I'd like to be able to set different theme color for light and dark mode. E.g my company has an accent color (bright yellow) that looks OK on black background, but on white background it's barely legible.

So I'm proposing introducing:

themeDark, in addition to them (there is already logo and logoDark)

[Salakar]

This seems reasonable, wdyt @Ehesp?

[Ehesp]

Started this here: https://github.com/invertase/docs.page/tree/feat/dark-theme

Need to properly try it out.

[bartekpacia]

Thanks so much! :)

Also while we're at it, it'd be nice to also add faviconDark (same case, my company's logo is black and white – https://patrol.leancode.co).