`corner-shape` utils

[geoffrey-eisenbarth]

Might be nice to pair these with the --border-radius vars.
https://css-tricks.com/what-can-we-actually-do-with-corner-shape/

[geoffrey-eisenbarth]

https://www.smashingmagazine.com/2026/03/beyond-border-radius-css-corner-shape-property-ui/

[geoffrey-eisenbarth]

https://caniuse.com/?search=corner-shape