add dropdown component

lib/utility/request.html

@@ -103,7 +103,7 @@ request.post('api/query', { id: 101 })
     .then(result => console.log(result.data));
 
 request.upload('api/upload', data, {
-    progress: (ev) => {
+    progress: ev => {
         console.log(`loaded: ${ev.loaded}, total: ${ev.total}`);
     }
 })