fix(list): use correct aria-orientation to improve accessibility

The `aria-orientation` attribute is simply not valid for `role="group"`
(which is used for checkboxes), according to the ARIA spec.
This is regardless of how the keyboard navigation actually works.

Author: Kiarokh

src/components/list/list-renderer.tsx

@@ -42,13 +42,26 @@ export class ListRenderer {
             <ul
                 class="mdc-deprecated-list"
                 role={role}
-                aria-orientation="vertical"
+                aria-orientation={this.getAriaOrientation(role)}
             >
                 {items.map(this.renderListItem)}
             </ul>
         );
     }
 
+    /**
+     * `aria-orientation` is valid for `listbox` and `radiogroup`,
+     * but not for group (used for checkboxes).
+     * @param role
+     */
+    private getAriaOrientation = (role: string) => {
+        if (role === 'listbox' || role === 'radiogroup') {
+            return 'vertical';
+        } else {
+            return null;
+        }
+    };
+
     /**
      * Determine which ListItem should have the `tab-index` attribute set,
      * and return the index at which that ListItem is located in `items`.