[ReactNative][MAdMan] Add type for image source, flowify AdsManagerObjectiveTypes

Libraries/Image/ImageSource.js

@@ -0,0 +1,17 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @providesModule ImageSource
+ * @flow
+ */
+'use strict';
+
+type ImageSource = {
+  uri: string;
+  isStatic: boolean;
+};