title: Element font-family must be declared
body: <p>when i open a project from github ,the folder from res folder has a xml resource product_famliy.xml but android studio has a error:</p>
  
  <pre><code>Information:Gradle tasks [clean, :app:generateDebugSources, :app:generateDebugAndroidTestSources, :app:mockableAndroidJar, :app:prepareDebugUnitTestDependencies]
  E:\googledownload\PaperPlane-master\app\src\main\res\font\product_family.xml
  Error:Error: Unsupported type 'font'
  Error:Execution failed for task ':app:mergeDebugResources'.
  &gt; E:\googledownload\PaperPlane-master\app\src\main\res\font\product_family.xml: Error: Unsupported type 'font'
  Information:BUILD FAILED
  Information:Total time: 21.311 secs
  Information:2 errors
  Information:0 warnings
  Information:See complete output in console 
  </code></pre>
  
  <hr>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;font-family xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"&gt;
  
      &lt;font
          android:fontStyle="normal"
          android:fontWeight="400"
          android:font="@font/product_sans_regular"
          app:fontStyle="normal"
          app:fontWeight="400"
          app:font="@font/product_sans_regular"/&gt;
  
      &lt;font
          android:fontStyle="italic"
          android:fontWeight="400"
          android:font="@font/product_sans_italic"
          app:fontStyle="italic"
          app:fontWeight="400"
          app:font="@font/product_sans_italic"/&gt;
  
  &lt;/font-family&gt;
  </code></pre>