list of items in the nav widget. Each array element represents a single
menu item which can be either a string or an array with the following structure:
- label: string, required, the nav item label.
- url: optional, the item's URL. Defaults to "#".
- visible: boolean, optional, whether this menu item is visible. Defaults to true.
- linkOptions: array, optional, the HTML attributes of the item's link.
- options: array, optional, the HTML attributes of the item container (LI).
- active: boolean, optional, whether the item should be on active state or not.
- items: array|string, optional, the configuration array for creating a [[Dropdown]] widget,
or a string representing the dropdown menu. Note that Bootstrap does not support sub-dropdown menus.
If a menu item is a string, it will be rendered directly without HTML encoding.