Add spec for Networking (#24892)

Summary:
Part of #24875, adds a spec for Networking. Since `sendRequest` methods are different for both platforms, I had to create 2 spec files as Flow would merge their definitions even when I added `Platform.OS` check

## Changelog

[General] [Added] - TM spec for Networking
Pull Request resolved: https://github.com/facebook/react-native/pull/24892

Reviewed By: RSNara

Differential Revision: D15543067

Pulled By: fkgozali

fbshipit-source-id: 2b91114dfa45e7899bbb139656a30a6fd52e31db

Libraries/Network/NativeNetworkingAndroid.js

@@ -0,0 +1,38 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+'use strict';
+
+import type {TurboModule} from 'RCTExport';
+import * as TurboModuleRegistry from 'TurboModuleRegistry';
+
+type Header = [string, string];
+
+export interface Spec extends TurboModule {
+  +sendRequest: (
+    method: string,
+    url: string,
+    requestId: number,
+    headers: Array<Header>,
+    data: Object,
+    responseType: Object, // TODO: Use stricter type.
+    useIncrementalUpdates: boolean,
+    timeout: number,
+    withCredentials: boolean,
+  ) => void;
+  +abortRequest: (requestId: number) => void;
+  +clearCookies: (callback: (result: boolean) => mixed) => void;
+
+  // RCTEventEmitter
+  +addListener: (eventName: string) => void;
+  +removeListeners: (count: number) => void;
+}
+
+export default TurboModuleRegistry.getEnforcing<Spec>('Networking');