ui: upgrade to webpack5

packages/ui-default/components/problem/create.page.js

@@ -1,7 +1,8 @@
-import { NamedPage } from 'vj/misc/Page';
+import $ from 'jquery';
 import { InfoDialog } from 'vj/components/dialog';
-import tpl from 'vj/utils/tpl';
+import { NamedPage } from 'vj/misc/Page';
 import i18n from 'vj/utils/i18n';
+import tpl from 'vj/utils/tpl';
 
 export default new NamedPage(['problem_create', 'problem_edit'], () => {
   $('input[name="pid"]').on('blur', () => {

packages/ui-default/components/problem/list.page.js

@@ -1,3 +1,4 @@
+import $ from 'jquery';
 import { AutoloadPage } from 'vj/misc/Page';
 
 export default new AutoloadPage('problemListPage', () => {