title: Capacitor doesn't recive android specific push-notifications
body: <p>I try to implement push-notifications to my Ionic4-Capacitor-App.</p>
  
  <p>In the app I have this code:</p>
  
  <pre class="lang-js prettyprint-override"><code>PushNotifications.register();
  PushNotifications.createChannel({ id: '1', description: '2019', importance: 2, name: '2019'});
  PushNotifications.addListener('pushNotificationReceived', (notification) =&gt; {
      console.debug(JSON.stringify(notification));
  });
  </code></pre>
  
  <p>With POSTMAN I try to send the following message:</p>
  
  <pre><code>{
      "to": "&lt;User-Token&gt;",
      "notification": {
          "title": "Default Title",
          "body": "Default Body"
      },
      "android": {
          "notification": {
              "title": "Android Title",
              "body": "Android Title",
              "channel_id": "1"
          }
      }
  }
  </code></pre>
  
  <p><a href="https://firebase.google.com/docs/reference/fcm/rest/v1/projects.messages" rel="nofollow noreferrer">Here is the documentation I used.</a></p>
  
  <p>The notification I recive has "Default Title" as a title and "Default Body" as a body.
  I expected it to have "Android Title" and "Android Body". Additionally, the notification is not pushed to channel 1, but to Miscellaneous.</p>
  
  <p>When I leave out the "root" notification part, no notification is displayed at all.</p>