Added ReactFeatureFlags shim for React Native (#11694)

* Added ReactFeatureFlags shim for React Native

* Fixed header license comment

Author: bvaughn

scripts/rollup/shims/react-native/ReactFeatureFlags.js

@@ -0,0 +1,16 @@
+/**
+ * Copyright (c) 2013-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @providesModule ReactFeatureFlags
+ */
+
+'use strict';
+
+var ReactFeatureFlags = {
+  debugRenderPhaseSideEffects: false,
+};
+
+module.exports = ReactFeatureFlags;