fix custom keys so they're spread across payload correctly

src/notifications/senders/AppleNotificationSender.ts

@@ -119,7 +119,7 @@ export class AppleNotificationSender {
             alert: notificationAlertArguments,
             sound: "default"
           },
-          customKeys,
+          ...customKeys,
         });
         req.write(payload);
         req.end();