code: function createOverlay(config) {
  
      var id = MODAL_OVERLAY_ID;
      var overlayText = config.text || MODAL_OVERLAY_TXT;
      var overlayClass = config.prefixClass + MODAL_OVERLAY_CLASS_SUFFIX;
      var overlayBackgroundEnabled = config.backgroundEnabled === 'disabled' ? 'disabled' : 'enabled';
  
      return '<span\n                    id="' + id + '"\n                    class="' + overlayClass + '"\n                    ' + MODAL_OVERLAY_BG_ENABLED_ATTR + '="' + overlayBackgroundEnabled + '"\n                    title="' + overlayText + '"\n                    >\n                    <span class="' + VISUALLY_HIDDEN_CLASS + '">' + overlayText + '</span>\n                  </span>';
    }
docs: Create the template for an overlay
  @param  {Object} config
  @return {String}