title: Icon is not displaying in push notifications in ionic 2
body: <p>I am trying to display app icon in notification. But it is displaying blank icon.</p>
  
  <p>I have given pushoptions as below:</p>
  
  <pre><code> const options: PushOptions = {
        android: {
          titleKey: 'App',
          sound: 'true',
          icon: 'res/drawable/notification_icon',
          topics: ['MyTopic']
        },
        ios: {
          alert: 'true',
          badge: false,
          sound: 'true'
        },
        windows: {}
      };
  </code></pre>
  
  <p>and copied the icon image as below which has resolution of 40*40px.</p>
  
  <pre><code>&lt;resource-file src="resources/notification_icon.png" target="res/drawable/notification_icon.png" /&gt;
  </code></pre>
  
  <p>Is there anything that I am missing?
  <img src="https://i.stack.imgur.com/INUQL.jpg" alt="enter image description here"></p>
  
  <p>Update:</p>
  
  <p>I followed this link : <a href="https://github.com/ionic-team/ionic-cli/issues/608" rel="nofollow noreferrer">https://github.com/ionic-team/ionic-cli/issues/608</a> and tried it by copying all the notification icon under resources/android/notification/drawable-XYZ/ic_stat_ac_unit.png to res/drawable-XYZ/ic_stat_ac_unit.png using the following statements:</p>
  
  <pre><code>&lt;resource-file src="resources/android/notification/drawable-hdpi/ic_stat_ac_unit.png" target="res/drawable-hdpi/ic_stat_ac_unit.png" /&gt;
          &lt;resource-file src="resources/android/notification/drawable-mdpi/ic_stat_ac_unit.png" target="res/drawable-mdpi/ic_stat_ac_unit.png" /&gt;
          &lt;resource-file src="resources/android/notification/drawable-xhdpi/ic_stat_ac_unit.png" target="res/drawable-xhdpi/ic_stat_ac_unit.png" /&gt;
          &lt;resource-file src="resources/android/notification/drawable-xxhdpi/ic_stat_ac_unit.png" target="res/drawable-xxhdpi/ic_stat_ac_unit.png" /&gt;
          &lt;resource-file src="resources/android/notification/drawable-xxxhdpi/ic_stat_ac_unit.png" target="res/drawable-xxxhdpi/ic_stat_ac_unit.png" /&gt;
  </code></pre>
  
  <p>and modified PushOptions in app.component.ts to :</p>
  
  <pre><code>android: {
      titleKey: 'App',
      sound: true,
      vibrate:true,
      icon: 'ic_stat_ac_unit',
      iconColor:'#343434',
      topics: ['MyTopic']
    }
  </code></pre>
  
  <p>Even this did not worked - Same Issue.</p>