Fixed #504 - Add id property to Menu

src/components/menu/Menu.d.ts

@@ -1,6 +1,7 @@
 import Vue from 'vue';
 
 export declare class Menu extends Vue {
+    id?: string;
     popup?: boolean;
     model?: any[];
     appendTo?: string;

src/views/menu/MenuDoc.vue

@@ -107,6 +107,12 @@ toggle(event) {
                             </tr>
 						</thead>
 						<tbody>
+                            <tr>
+                                <td>id</td>
+                                <td>string</td>
+                                <td>null</td>
+                                <td>Unique identifier of the element.</td>
+                            </tr>
                             <tr>
                                 <td>model</td>
                                 <td>array</td>