[ReactNative] Open source ProgressBarAndroid, remove example from the RN launcher

Libraries/Components/ProgressBarAndroid/ProgressBarAndroid.ios.js

@@ -0,0 +1,8 @@
+/**
+ * Copyright 2004-present Facebook. All Rights Reserved.
+ *
+ * @providesModule ProgressBarAndroid
+ */
+'use strict';
+
+module.exports = require('UnimplementedView');