Sidebar custom HTML properties

type	(string) required, the item type, set it to "customHTML". If not specified - the "navItem" type is applied by default.
id	(string, number) the id of an item, auto-generated if not set
parent	(string) the parent of the item
html	(string) a string with HTML that should be inserted into the item
css	(string|string[]) adds style classes
hidden	(boolean) defines whether an item is hidden