fix(typeahead): add variable which was missed in MR #5547

adding variable `list` which was added in host Object as `[attr.aria-autocomplete]: 'list'` but was not defined.
Modules/Libraries which uses AoT compilation for their build gets fatal error due to this.

this will fix let AoT builds to work properly which was introduced in MR #5547

Author: Dharit Desai

src/typeahead/typeahead.directive.ts

@@ -151,6 +151,7 @@ export class TypeaheadDirective implements OnInit, OnDestroy {
 
   activeDescendant: string;
   isOpen = false;
+  list = 'list';
   _container: TypeaheadContainerComponent;
   isActiveItemChanged = false;
   isFocused = false;