Fixed #367 - Ability to activate PanelMenu item declaratively or programmatically

api-generator/components/panelmenu.js

@@ -4,6 +4,12 @@ const PanelMenuProps = [
         type: "array",
         default: "null",
         description: "An array of menuitems."
+    },
+    {
+        name: "expandedKeys",
+        type: "array",
+        default: "null",
+        description: "A map of keys to represent the expansion state in controlled mode."
     }
 ];