title: Open webp file with Pillow
body: <p>On an Anaconda set up, I want to run following simple code:</p>
  <pre class="lang-py prettyprint-override"><code>from PIL import Image
  img = Image.open('test.webp')
  </code></pre>
  <p>This works on my Linux machine, but on Windows:</p>
  <pre><code>UserWarning: image file could not be identified because WEBP support not installed
    warnings.warn(message)
  ---------------------------------------------------------------------------
  UnidentifiedImageError                    Traceback (most recent call last)
  &lt;ipython-input-3-79ee787a81b3&gt; in &lt;module&gt;
  ----&gt; 1 img = Image.open('test.webp')
  
  ~\miniconda3\lib\site-packages\PIL\Image.py in open(fp, mode, formats)
     3028     for message in accept_warnings:
     3029         warnings.warn(message)
  -&gt; 3030     raise UnidentifiedImageError(
     3031         &quot;cannot identify image file %r&quot; % (filename if filename else fp)
     3032     )
  
  UnidentifiedImageError: cannot identify image file 'test.webp'
  </code></pre>
  <p>I do have the <code>libwebp</code> package installed, and <code>libwebp.dll</code> is present in the <code>Library\bin</code> directory of my Anaconda set up.</p>
  <p>Any idea?</p>