feat(timeline): Add item data as argument to the template function (#2799)

lib/timeline/component/item/Item.js

@@ -342,7 +342,7 @@ Item.prototype._updateContents = function (element) {
 
   if (this.options.template) {
     templateFunction = this.options.template.bind(this);
-    content = templateFunction(itemData, element);
+    content = templateFunction(itemData, element, this.data);
   } else {
     content = this.data.content;
   }