How to show support for font-variation-settings within @font-face?

Related but different to #4010, https://caniuse.com/#feat=variable-fonts shows info about the regular `font-variation-settings` property. 

But in CSS4, that property can be set within an @font-face rule (https://www.w3.org/TR/css-fonts-4/#font-rend-desc) and currently that (lack of) support isn't clearly conveyed on the caniuse page linked above.