refactor(aria/combobox): Add accessors for pattern properties

Author: adolgachev

src/aria/combobox/combobox.ts

@@ -82,9 +82,15 @@ export class Combobox<V> {
   /** The value of the first matching item in the popup. */
   readonly firstMatch = input<V | undefined>(undefined);
 
+  /** The id of the current active item. */
+  readonly activedescendant = computed(() => this._pattern.activedescendant());
+
   /** Whether the combobox is expanded. */
   readonly expanded = computed(() => this._pattern.expanded());
 
+  /** The currently highlighted item in the combobox. */
+  readonly highlightedItem = computed(() => this._pattern.highlightedItem());
+
   /** Input element connected to the combobox, if any. */
   readonly inputElement = computed(() => this._pattern.inputs.inputEl());