added notification permission for android

android/src/main/java/com/joshblour/reactnativepermissions/ReactNativePermissionsModule.java

 import android.net.Uri;
 import android.provider.Settings;
 import android.support.v4.app.ActivityCompat;
+import android.support.v4.app.NotificationManagerCompat;
 import android.support.v4.content.ContextCompat;
 import android.support.v4.content.PermissionChecker;
 
 
   public enum RNType {
     LOCATION,
+    NOTIFICATION,
     CAMERA,
     MICROPHONE,
     CONTACTS,
     super(reactContext);
     this.reactContext = reactContext;
     mPermissionsModule = new PermissionsModule(this.reactContext);
+    this.notificationManagerCompat = NotificationManagerCompat.from(reactContext);
   }
 
   @Override
       return;
     }
 
+    if(permission == 'notification') {
+      if (this.notificationManagerCompat.areNotificationsEnabled()) {
+        promise.resolve("authorized");
+      } else {
+        promise.resolve("denied");
+      }
+      return;
+    }
+
     int result = PermissionChecker.checkSelfPermission(this.reactContext, permission);
     switch (result) {
       case PermissionChecker.PERMISSION_DENIED:
       case PHOTOS:
         return Manifest.permission.READ_EXTERNAL_STORAGE;
       default:
-        return null;
+        return permission;
     }
   }