Renders the content of the custom list item in the MultiSelect
(see example).
The template context is set to the current component.
To get a reference to the current text that is typed by the
user, use the let-customItem directive.

The CustomItemTemplate directive can only be used with the MultiSelect component.

selector: 'my-app',
template: `
 <kendo-multiselect [data]="listItems" [allowCustom]="true">
   <ng-template kendoMultiSelectCustomItemTemplate let-customItem>
     <span>New Item: {{customItem}}</span>
class AppComponent {
  public listItems: Array<string> = ["Item 1", "Item 2", "Item 3", "Item 4"];