title: react-native-push-notification can not build in android
body: <p>I'll be using react-native-push-notification for notifications in my app but when I use this library it gives me error like this.....</p>
  
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  <pre class="snippet-code-js lang-js prettyprint-override"><code>&gt; Task :react-native-push-notification:compileDebugJavaWithJavac FAILED
  E:\AndroidNotify\node_modules\react-native-push-notification\android\src\main\java\com\dieam\reactnativepushnotification\modules\RNPushNotificationHelper.java:7: error: cannot find symbol
  import android.app.NotificationChannel;
                    ^
    symbol:   class NotificationChannel
    location: package android.app
  E:\AndroidNotify\node_modules\react-native-push-notification\android\src\main\java\com\dieam\reactnativepushnotification\modules\RNPushNotificationHelper.java:480: error: cannot find symbol
          if (Build.VERSION.SDK_INT &lt; Build.VERSION_CODES.O)
                                                         ^
    symbol:   variable O
    location: class VERSION_CODES
  E:\AndroidNotify\node_modules\react-native-push-notification\android\src\main\java\com\dieam\reactnativepushnotification\modules\RNPushNotificationHelper.java:488: error: cannot find symbol
          int importance = NotificationManager.IMPORTANCE_DEFAULT;
                                              ^
    symbol:   variable IMPORTANCE_DEFAULT
    location: class NotificationManager
  E:\AndroidNotify\node_modules\react-native-push-notification\android\src\main\java\com\dieam\reactnativepushnotification\modules\RNPushNotificationHelper.java:489: error: cannot find symbol
          NotificationChannel channel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, name, importance);
          ^
    symbol:   class NotificationChannel
    location: class RNPushNotificationHelper
  E:\AndroidNotify\node_modules\react-native-push-notification\android\src\main\java\com\dieam\reactnativepushnotification\modules\RNPushNotificationHelper.java:489: error: cannot find symbol
          NotificationChannel channel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, name, importance);
                                            ^
    symbol:   class NotificationChannel
    location: class RNPushNotificationHelper
  Note: Some input files use or override a deprecated API.
  Note: Recompile with -Xlint:deprecation for details.
  5 errors</code></pre>
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