Add font-size-adjust (#748)

Co-authored-by: Daniel D. Beck <[email protected]>

Author: foolip

feature-group-definitions/font-size-adjust.yml

@@ -0,0 +1,9 @@
+name: font-size-adjust
+description: The `font-size-adjust` CSS property preserves apparent text size, regardless of the font used, by scaling fonts to the same size with respect to a specific metric, such as x-height. This can help make fallback fonts look the same size.
+spec: https://drafts.csswg.org/css-fonts-5/#font-size-adjust-prop
+caniuse: font-size-adjust
+compat_features:
+  - css.properties.font-size-adjust
+  - css.properties.font-size-adjust.from-font
+  - css.properties.font-size-adjust.none
+  - css.properties.font-size-adjust.two-values