chore: update example app for Flutter 3.10

[OutdatedGuy]

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[OutdatedGuy]

@jonbhanson, ran GitHub actions successfully

[bartekpacia]

Please also add namespace to build.gradle in the android and example/android directories.

Currently this package causes Gradle builds using AGP v8 to fail with:

$ ./gradlew :app:assembleDebug

FAILURE: Build failed with an exception.

* What went wrong:
A problem occurred configuring project ':flutter_native_splash'.
> Could not create an instance of type com.android.build.api.variant.impl.LibraryVariantBuilderImpl.
   > Namespace not specified. Please specify a namespace in the module's build.gradle file like so:

     android {
         namespace 'com.example.namespace'
     }

     If the package attribute is specified in the source AndroidManifest.xml, it can be migrated automatically to the namespace value in the build.gradle file using the AGP Upgrade Assistant; please refer to https://developer.android.com/studio/build/agp-upgrade-assistant for more information.

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 913ms

[OutdatedGuy]

@bartekpacia, I'll create a separate PR to add support for AGP 8.

Looks like the support is already added in this PR, just have to wait till @jonbhanson publishes new release with these changes.