Fix class selector in Fully Featured example

The global selector must use a proper CSS class selector to target the custom-dropzone class correctly.

Author: tascodes

stories/views/FullyFeaturedDropzoneView.svelte

@@ -22,7 +22,7 @@
 </script>
 
 <style>
-  :global(custom-dropzone) {
+  :global(.custom-dropzone) {
   }
 </style>