Ionic resource icon for Android push notifications

Hey Ionic!

Would be nice if we could automatically set an icon for multiple resolutions as a custom push notification icon, as an addition to the app's icon & splash screen.

No files, tests, or entry points are named. Start by locating the Ionic CLI's Android resource generation and push-notification configuration, then define how multi-resolution notification icons should be supplied and verify the result in an Android app.

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