So `app://` is defined to use `app://<package_name>/<relative_path>` to load resources, but the `package_name` must be itself's package name? I really don't understand the purpose of this design. If it's use to load the resource within the app, why put package name here, isn't `app://<relative_path>` more reasonable? Web developers even don't care which package his app will be packed in, the feature force them to aware of the package and don't allow them to use across package? I can't understand the intention.