Improve & optimize regex detection

Fixes #229

src/JS.php

@@ -238,7 +238,7 @@ class JS extends Minify
         // closing the regex)
         // then also ignore bare `/` inside `[]`, where they don't need to be
         // escaped: anything inside `[]` can be ignored safely
-        $pattern = '\\/([^\\[\\/\\\\]*+|(\\\\.)*+|\\[([^\\]\\\\]|\\\\.)*\\])+\\/[gimy]*';
+        $pattern = '\\/(?:[^\\[\\/\\\\]+|(?:\\\\.)+|(?:\\[(?:[^\\]\\\\]+|(?:\\\\.)+)+\\])+)++\\/[gimy]*';
 
         // a regular expression can only be followed by a few operators or some
         // of the RegExp methods (a `\` followed by a variable or value is