Add getLaunchAppNotification API

Change Log：

• unify remote notifcation field, iOS will add extras field just like android. NOTICE: If you extras-keys contain extras key, it will move into extras field, so you need adjust you code like that:

JPushModule.addReceiveNotificationListener( notification => {
 // old:
  const oldExtrasString = notifcation.extras;

  // new:
  const newExtrasString = notification.extras.extras;
})

Add API：

• getLaunchAppNotification