Add jest mock for 'PushNotificationManager'

Summary:
`PushNotificationIOS` is a library that makes use of the
`PushNotificationManager` native module.
This commit adds a jest mock for its native module so that code that
uses `PushNotificationIOS` can be tested using jest.

In order to enable behaviour in unit tests it is possible to replace or
overwrite the mock implementation, see the [jest guide on
mocks](https://facebook.github.io/jest/docs/mock-functions.html).
By doing something similar to:
```javascript
import { NativeModules } from 'react-native';
const { PushNotificationManager } = NativeModules;
// mock 'checkPermissions' to return a different value than the default:
PushNotificationManager.checkPermissions.mockImplementationOnce((callback) => {
    // execute callback in next tick to enable async behaviour
    process.nextTick(() => callback({
        alert: false,
        badge: false,
        sound: false
    }));
});
// execute unit tests for code that makes use of 'PushNotificationIOS'
```
Closes https://github.com/facebook/react-native/pull/13410

Differential Revision: D5043904

Pulled By: cpojer

fbshipit-source-id: 11e73cd215ba6854d06f4ac7a5aea0ab4be26584

jest/setup.js

@@ -156,6 +156,24 @@ const mockNativeModules = {
     addListener: jest.fn(),
     removeListeners: jest.fn(),
   },
+  PushNotificationManager: {
+    presentLocalNotification: jest.fn(),
+    scheduleLocalNotification: jest.fn(),
+    cancelAllLocalNotifications: jest.fn(),
+    removeAllDeliveredNotifications: jest.fn(),
+    getDeliveredNotifications: jest.fn(callback => process.nextTick(() => [])),
+    removeDeliveredNotifications: jest.fn(),
+    setApplicationIconBadgeNumber: jest.fn(),
+    getApplicationIconBadgeNumber: jest.fn(callback => process.nextTick(() => callback(0))),
+    cancelLocalNotifications: jest.fn(),
+    getScheduledLocalNotifications: jest.fn(callback => process.nextTick(() => callback())),
+    requestPermissions: jest.fn(() => Promise.resolve({alert: true, badge: true, sound: true})),
+    abandonPermissions: jest.fn(),
+    checkPermissions: jest.fn(callback => process.nextTick(() => callback({alert: true, badge: true, sound: true}))),
+    getInitialNotification: jest.fn(() => Promise.resolve(null)),
+    addListener: jest.fn(),
+    removeListeners: jest.fn(),
+  },
   SourceCode: {
     scriptURL: null,
   },