Update README.md

Author: mfranzke

packages/stylelint-config-if-function/README.md

@@ -1,6 +1,6 @@
 # stylelint-config-if-function
 
-A shareable [Stylelint](https://github.com/stylelint/stylelint) config to support the experimental CSS `if()` function syntax.
+A shareable [Stylelint](https://github.com/stylelint/stylelint) config to support the experimental [CSS `if()` function](https://developer.mozilla.org/en-US/docs/Web/CSS/if) syntax.
 
 ## Installation