Merge pull request 4GeeksAcademy#33 from dariatsvetkova/patch-1

Update index.js

Author: alesanchezr

exercises/03.5-alert-component/index.js

@@ -1,5 +1,6 @@
 import React from "react";
 import ReactDOM from "react-dom";
+import PropTypes from "prop-types";
 
 /**
  * here you have declare your Alert component and return