make event forwarding example work initially

site/content/tutorial/05-events/05-event-forwarding/app-a/Outer.svelte

@@ -1,5 +1,12 @@
 <script>
 	import Inner from './Inner.svelte';
+	import { createEventDispatcher } from 'svelte';
+
+	const dispatch = createEventDispatcher();
+
+	function forward(event) {
+		dispatch('message', event.detail);
+	}
 </script>
 
-<Inner/>
+<Inner on:message={forward}/>