fix: typo in deferred-transitions tutorial (sveltejs#600)

Author: langpavel

apps/svelte.dev/content/tutorial/02-advanced-svelte/05-advanced-transitions/01-deferred-transitions/+assets/app-a/src/lib/App.svelte

@@ -24,7 +24,7 @@
 
 			todos.push({
 				done: false,
-				text: e.currentTarget.value
+				description: e.currentTarget.value
 			});
 
 			e.currentTarget.value = '';