[CSS Gap Decorations] support gradients and images as alternative to solid colors

[Th3S4mur41]

Solid color has been a limitation of borders for quite some time. Border image now opens new opportunities for more creative borders.

It would be great to get similar options for columns and row rules.
Something like column-rule-image and row-rule-image maybe to keep the syntax like border and keep low cognitive load?!

[kbabbitt]

Thanks for the feedback!

This is something we're interested in exploring in a future level of the spec. It would be a little more challenging than border-image, because in addition to corners, you also need to consider T intersections and cross intersections. Certainly possible, but sufficiently more complex that we wanted to focus on getting solid color decorations into authors' hands first.