Support Google Play Package Installer

[peer-f]

Hi,
thank you for this helpful package and for supporting both new and old Android versions. Most of the packages out there don't work with newer Android API levels.

We use Firebase App Distribution for testing development and release versions of our app on Android.

Your package detects this correctly by returning 'com.google.android.packageinstaller'.

Maybe you could add googlePlayInstaller to the Installer enum.

Beyond that it would be interesting to know what is returned when using a closed track on Google Play.