Don't use pointer cursor on disabled buttons by default (#5772)

Author: adamwathan

src/css/preflight.css

@@ -317,6 +317,13 @@ button,
   cursor: pointer;
 }
 
+/*
+Make sure disabled buttons don't get the pointer cursor.
+*/
+:disabled {
+  cursor: default;
+}
+
 /*
 1. Make replaced elements `display: block` by default. (https://github.com/mozdevs/cssremedy/issues/14)
 2. Add `vertical-align: middle` to align replaced elements more sensibly by default. (https://github.com/jensimmons/cssremedy/issues/14#issuecomment-634934210)