[css-forms-1] Have 2 slider-fill pseudos?

[nt1m]

It would probably be beneficial to have ::slider-fill-upper and ::slider-fill-lower (names to be bikeshed) as @thebabydino describes here: #4410 (comment)

There's also the multi-range proposal in Open UI: https://open-ui.org/components/enhanced-range-input.explainer/ which might good to coordinate with.