add aria properties to top menu

src/components/TopBar.vue

@@ -37,7 +37,10 @@
       </v-toolbar-items>
       
 
-            <v-btn id="top_menu" width="96px" v-if="$route.name != 'about'" aria-labelledby="menu_label" text @click.native="menuOpen = !menuOpen">
+            <v-btn id="top_menu" 
+                   :aria-expanded="menuOpen? 'true' : 'false'"
+                   aria-haspopup="menu"
+                   width="96px" v-if="$route.name != 'about'" aria-labelledby="menu_label" text @click.native="menuOpen = !menuOpen">
               <span id="menu_label">{{$t('menu.title')}}</span><v-icon right>{{menuOpen? 'close' : 'menu'}}</v-icon></v-btn>
         <v-divider vertical/>