Add fragment to make example reactive (#976)

Author: edemaine

src/routes/configuration/typescript.mdx

@@ -584,7 +584,9 @@ return <div>{user()?.name}</div>;
 
 return (
 	<div>
-		<Show when={user()}>{(nonNullishUser) => nonNullishUser().name}</Show>
+		<Show when={user()}>{(nonNullishUser) => <>
+			{nonNullishUser().name}
+		</>}</Show>
 	</div>
 );
 ```