Add a FlutterView level integration example on Android for add-to-app (#632)

add_to_app/android_view/README.md

@@ -0,0 +1,14 @@
+# android_view
+
+An example of an Android app that integrates a Flutter add-to-app module at a
+view level. For more information on how to use it, see the [README](../README.md)
+file located in the [/add_to_app](/add_to_app) directory of this repo.
+
+## Getting Started
+
+For more information about Flutter, check out
+[flutter.dev](https://flutter.dev).
+
+For instructions on how to integrate Flutter modules into your existing
+applications, see Flutter's
+[add-to-app documentation](https://flutter.dev/docs/development/add-to-app).