fix: filenames for code examples

Author: jouni

articles/hilla/guides/routing.adoc

@@ -67,6 +67,7 @@ Sometimes, you may need to create routes that accept dynamic parameters, such as
 
 For example, create a file named `{productId}.tsx` in the `src/main/frontend/views/products/` directory with the following content:
 
+.`{productId}.tsx`
 [source,tsx]
 ----
 import { useParams } from 'react-router-dom';
@@ -119,6 +120,7 @@ For adding a layout, create a view file named `@layout.tsx` in the views directo
 
 The following example defines the main layout with the drawer and the main menu:
 
+.`@layout.tsx`
 [source,tsx]
 ----
 import { AppLayout } from '@vaadin/react-components/AppLayout.js';