feat(list): add activeItem getter

list/internal/list-controller.ts

@@ -138,6 +138,14 @@ export class ListController<Item extends ListItem> {
     return items;
   }
 
+  /**
+   * Retrieves the first activated item of the array of items regarding
+   * controller's configuration.
+   */
+  get activeItem() {
+    return getActiveItem(this.items, this.isActivatable);
+  }
+
   /**
    * Handles keyboard navigation. Should be bound to the node that will act as
    * the List.

list/internal/list.ts

@@ -90,4 +90,14 @@ export class List extends LitElement {
   activatePreviousItem(): ListItem | null {
     return this.listController.activatePreviousItem();
   }
+
+  /**
+   * Retrieves the first activated item of the array of items.
+   *
+   * @return A record of the first activated item including the item and the
+   *     index of the item or `null` if none are activated.
+   */
+  get activeItem() {
+    return this.listController.activeItem;
+  }
 }