Added TODO item

README.md

@@ -118,3 +118,5 @@ TODO / bugs
   produces inequivalent CSS, and could be fixed by unfolding each generic
   border declaration into four direction-specific ones, and sybsequently
   generating the shortest possible representation of the resulting box model.
+- `border:none` could be `border:0`, or in general any shorthand that has both
+  a `style` and `width` property should be transformed from `none` into `0`.