Docs(web-twig): Add stories to file structure example

packages/web-twig/CONTRIBUTING.md

@@ -21,6 +21,8 @@ This is an example of a typical file structure of a component:
     └── Resources
         └── components
             └── <ComponentName>
+                ├── stories - Component stories
+                ├── <ComponentName>.stories.twig - Template rendered in demo app
                 ├── <ComponentName>.twig — Twig component
                 └── README.md — documentation of the component
 ```