Add docs explaining how to enable Material 3 design on Android with `UseMaterial3`

Material 3 design is currently not enabled by default on the Android platform. To apply Material 3 theming and components, the UseMaterial3 build property must be explicitly enabled. Without this setting, the application continues to use Material 2 styles, which can lead to missing Material 3 features.

To enable Material 3 design on Android, set the `UseMaterial3` build property to true.