fix: Deprecated imperative apply of Flutter's Gradle plugins

[yuruyuri16]

Description
Since Flutter 3.16, Flutter's Gradle plugins are now applied using the Plugin DSL syntax instead of the legacy script syntax.

More info here

Steps To Reproduce

1. Create a very good flutter app
2. Run in android and some deprecation messages will pop up.

Expected Behavior
Run with no warnings.

Screenshots

[alestiago]

I was able to reproduce this issue when running on a physical Android device running on Android 10.

You are applying Flutter's app_plugin_loader Gradle plugin imperatively using the apply script method, which is deprecated and will be removed in a future release. Migrate to applying Gradle plugins with the declarative plugins block: https://flutter.dev/go/flutter-gradle-plugin-apply

You are applying Flutter's main Gradle plugin imperatively using the apply script method, which is deprecated and will be removed in a future release. Migrate to applying Gradle plugins with the declarative plugins block: https://flutter.dev/go/flutter-gradle-plugin-apply

[alestiago]

Closing this issue, since it is being moved to very_good_templates, VeryGoodOpenSource/very_good_templates#75.