Add Namespace Support for Android Gradle Plugin (AGP) 8.x Compatibility #391

The flutter_mapbox_navigation package is not compatible with Android Gradle Plugin (AGP) 8.x due to the absence of a namespace property in the android/build.gradle file. Starting with AGP 8.0.0, the namespace property is required for all Android modules to decouple the internal namespace from the AndroidManifest.xml file.

Steps to Reproduce:

1. Add flutter_mapbox_navigation version 0.2.2 to a Flutter project.
2. Update the project's Android Gradle Plugin to version 8.x (e.g., 8.1.1 or later).
3. Attempt to sync or build the project.

Observed Behavior:
The build fails with the following error:

A problem occurred configuring project ':flutter_mapbox_navigation'.
> Could not create an instance of type com.android.build.api.variant.impl.LibraryVariantBuilderImpl.
   > Namespace not specified. Specify a namespace in the module's build file: /Users/<username>/.pub-cache/hosted/pub.dev/flutter_mapbox_navigation-0.2.2/android/build.gradle. See https://d.android.com/r/tools/upgrade-assistant/set-namespace for information about setting the namespace.

Expected Behavior:
The project should build successfully with AGP 8.x when using the flutter_mapbox_navigation package.