title: Dragtozoom both horizontal and vertical
body: <p>Working on a google chart and by dragging to horizontal it zooms. So wondering if its possible to also drag to vertical with the horizontal. I tried to copy the explorer and change horizontal to vertical, that didn't work out.</p>
  
  <pre><code>explorer: { actions: ['dragToZoom', 'rightClickToReset'], 
                      axis: 'horizontal' },
  
  explorer: { actions: ['dragToZoom', 'rightClickToReset'], 
                      axis: 'vertical' },
  </code></pre>