Add a comment to explain why the polyfill service needs to not be min…

…ified

ps. it only solved half the issue

public/index.html

@@ -38,6 +38,7 @@
   }
 };
 </script>
+<!-- We NEED to use a non minified version of the polyfill service as the minified version causes an error in PhantomJS: "Attempting to configurable attribute of unconfigurable property." -->
 <script src="https://ft-polyfill-service.herokuapp.com/v2/polyfill.js?features=es6&unknown=polyfill" crossorigin="anonymous"></script>
 <link rel="stylesheet" href="//cdn.jsdelivr.net/chartist.js/latest/chartist.min.css" />