title: Error when trying to build cordova app with adaptive icons
body: <p>When trying to add an adaptive icon in config.xml I get the following error when trying to build</p>
  
  <blockquote>
    <p>One of the following attributes are set but missing the other for the density type: ldpi, mdpi, hdpi, xhdpi, xxhdpi, xxxhdpi. Please ensure that all require attributes are defined.</p>
  </blockquote>
  
  <p>My code is:</p>
  
  <pre><code>&lt;platform name="android"&gt;
      &lt;resource-file src="res/icon/android/colors.xml" target="/app/src/main/res/values/colors.xml" /&gt;
      &lt;icon background="@color/background" density="ldpi" foreground="res/icon/android/ldpi-foreground.png" /&gt;
      &lt;icon background="@color/background" density="mdpi" foreground="res/icon/android/mdpi-foreground.png" /&gt;
      &lt;icon background="@color/background" density="hdpi" foreground="res/icon/android/hdpi-foreground.png" /&gt;
      &lt;icon background="@color/background" density="xhdpi" foreground="res/icon/android/xhdpi-foreground.png" /&gt;
      &lt;icon background="@color/background" density="xxhdpi" foreground="res/icon/android/xxhdpi-foreground.png" /&gt;
      &lt;icon background="@color/background" density="xxxhdpi" foreground="res/icon/android/xxxhdpi-foreground.png" /&gt;
  &lt;/platform&gt;
  </code></pre>
  
  <p>I'm using cordova-android 8.0.0</p>