[css-cascade] Add CanIUse panels

[cvrebert]

Bikeshed has a feature to include CanIUse info panels in specs. (Example; Example commit)

I wonder if css-cascade would consider using this feature? Here are the spec anchors and corresponding CanIUse features for css-cascade:

CSS spec URL	CanIUse feature URL
https://drafts.csswg.org/css-cascade/#all-shorthand	https://caniuse.com/#feat=css-all
https://drafts.csswg.org/css-cascade/#inherit-initial	https://caniuse.com/#feat=css-unset-value
https://drafts.csswg.org/css-cascade/#valdef-all-revert	https://caniuse.com/#feat=css-revert-value
https://drafts.csswg.org/css-cascade/#initial	https://caniuse.com/#feat=css-initial-value

[tabatkins]

Thanks for the listing of features!