Update builder.html

builder.html

@@ -4,7 +4,11 @@
     <meta charset="utf-8">
     <title>GrapesJS</title>
     <link rel="stylesheet" href="https://unpkg.com/grapesjs/dist/css/grapes.min.css">
+ 
     <script src="https://unpkg.com/grapesjs"></script>
+
+   <script src="path/to/grapesjs-custom-code.min.js"></script>
+    
     <style>
       body,
       html {