code: public ListTemplateElementBuilder addUrlButton(String title, String url) {
  		Button button = ButtonFactory.createUrlButton(title, url);
  		this.element.addButton(button);
  		return this;
  	}
docs: Adds a button which redirects to an URL when clicked to the current
  {@link ListTemplateElement}. There can be at most 3 buttons per element.
  
  @param title
  the button label.
  @param url
  the URL to whom redirect when clicked.
  @return this builder.