title: Highcharts: Add a custom image button
body: <p>I want to add and image button on highcharts.
  So far, I have successfully created a image button and have attached a click event on it.
  But problem is that, the image (sun.png) is on left side of chart and image button is right aligned ( the default position of toolbar). Any fix for this ?</p>
  
  <pre><code>exporting: {
      buttons: {
          popUpBtn: {
              symbol: 'url(images/sun.png)',
              _titleKey: 'popUpBtnTitle',
              x: -10,
              symbolFill: '#B5C9DF',
              hoverSymbolFill: '#779ABF',
              onclick: function () {
                  alert('ad');
                  popUpChart($(this));
              }
          },
          exportButton: {
              enabled: false
          },
          printButton: {
              enabled: false
          }
  
      }
  }
  </code></pre>
  
  <p>Also, if there are other methods to add an image in chart which have click event, those methods are welcomed too.</p>