[Enhancements] Add the possibility to setup an header inside the js initialisation of DropDown

[Maregas]

According to the documentation: https://semantic-ui.com/modules/dropdown.html#header if a div inside the menu of the dropdown is defined as an "header" and not an "item" it will be disabled with a specific design. Could it be possible to add the option on the JS initialization like the option disabled, for example?

.dropdown({ values: [ { name:"Header", header: true },