title: Clustering custom html markers with mapbox-gl-js
body: <p>I'm using the mapbox-gl-js API and I'm using it with react to create some custom markers as follows:</p>
  
  <pre><code>        let div = document.createElement('div');
          let marker = new mapboxgl.Marker(div, {
              offset: [ -20, 80 ]
          });
  
          marker.setLngLat(person.geometry.coordinates);
  
          render(
              &lt;MapPersonIcon /&gt;,
              div,
              () =&gt; {
                  marker.addTo(map);
              }
          );
  </code></pre>
  
  <p><img src="https://files.gitter.im/hdrdavies/JustMe/U5Qh/Screen-Shot-2016-08-17-at-17.30.53.png" alt="result"></p>
  
  <p>This worked great. However I would now like to cluster these markers, producing the same affect as the functionality found with layers i.e. </p>
  
  <p><a href="https://www.mapbox.com/mapbox-gl-js/example/cluster/" rel="noreferrer">https://www.mapbox.com/mapbox-gl-js/example/cluster/</a></p>
  
  <p><img src="https://files.gitter.im/hdrdavies/JustMe/pJ8u/Screen-Shot-2016-08-17-at-17.28.38.png" alt="clusters"></p>
  
  <p>Does anyone know whether this is possible (hopefully with custom clusters too) or whether it will be available in an upcoming release?</p>