Add utilities for scrollbar-color

[lukewarlow]

Add utilities for the scrollbar-color CSS property.

Currently only supported by Firefox but coming soon to Chromium, and not as relevant to Safari as Apple platforms use overlay scrollbars by default.

I'm imagining something like

class="thumb-red-200 track-white" which would generate something like scrollbar-color: #FECACA white;.

I'm thinking perhaps they should have a scrollbar- prefix to avoid ambiguity in case of future CSS properties for styling range inputs for example.

To my knowledge this would be the first utilities where two are required to be combined together to generate valid CSS?

So maybe track could default to something that makes sense.

[lukewarlow]

In case anyone comes across this discussion looking for a solution I've made an npm package with a plugin for scrollbar color (along with gutter and width) utilities. See https://github.com/lukewarlow/tailwind-scrollbar-utilities

[lukewarlow]

Chromium intent to ship: https://groups.google.com/a/chromium.org/g/blink-dev/c/PkEsMirl2zE