Implement Bottom Nav Bar using Stacked and Navigation Service

We were working on custom bottom navigation bar using `GestureDetector` to navigate through different states. But it's increasing the Firebase Reads every the screen is built. With your recent update where `IndexTrackingViewModel` is included, we want to understand how to implement with a multi-route App and NavigationService.

In our scenario we have Splash Screen Navigates to HomeScreen. Bottom Navigation is visible in three screens, each of the following screen uses a custom stateless class `CustomBottomNavigation` which returns `BottomNavigationBar`.
1. HomeScreen with Multi Widgets and Navigation Text Links
2. FirebaseList Screen with Sliver List (OnTap of List Item) Firebase List Item Detail Screen.
3. User Screen with Sliver List (OnTap of List Item) Firebase List Item Detail Screen.

Right now the navigation is controlled using `Router` as explained in your tutorial.

Do we have to extend `IndexTrackingViewModel` to each of the above three viewmodels which are currently extending `BaseModel`?

Comienza leyendo los puntos de entrada mencionados, IndexTrackingViewModel, BaseModel, Router y CustomBottomNavigation, y después sigue los flujos de navegación de HomeScreen, FirebaseList y UserScreen. La tarea estaría terminada cuando exista un enfoque de navegación inferior con múltiples rutas, claramente documentado o funcional, que evite reconstrucciones innecesarias de pantallas y lecturas de Firebase, incluida una decisión sobre cómo los tres viewmodels utilizan IndexTrackingViewModel.

Escrito por el modelo de indexación a partir del texto del issue.