Support CSS feature `prefers-color-scheme`

[peterbecich]

https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-color-scheme

The prefers-color-scheme CSS media feature is used to detect if the user has requested a light or dark color theme.

GitHub and Google support this feature.

[kandji-edwin]

Are there color palettes for light and dark themes that would be used for this?

[peterbecich]

@kandji-edwin , I haven't found any so I took the existing colors and guessed: #1008 (comment)

[peterbecich]

Improvement: #1281