title: Set the anchor of the Marker
body: <p>We are trying to use a custom icon for our marker using react-google-maps.</p>
  
  <p>It is working, however the "anchor" of the icon appears to default to the top left of the pin (0,0) which does not work with our icon.</p>
  
  <p>I can see that using the google-maps-api directly there is a .Point:</p>
  
  <pre><code>anchor: new google.maps.Point(17, 34)
  </code></pre>
  
  <p>But we can't see how to set this within the react-google-maps components.</p>
  
  <p>Here is our code:</p>
  
  <pre><code>const icon = {
    path: 'M32,0C20.8,0...',
    fillColor: '#444',
    fillOpacity: 1,
    strokeWeight: 0,
    scale: 0.75
  };
  
  ....
  
  &lt;Marker position={marker.position} key={index} icon={icon} /&gt;
  </code></pre>
  
  <p>Ideally there would be some sort of anchor key we can set directly in our Icon object.</p>
  
  <p>Any help would be greatly appreciated.</p>