js2ts: index(login)

- fix-workaround: popper 로드

hwe/ts/common_legacy.ts

@@ -1,6 +1,8 @@
 import { unwrap } from "./util/unwrap";
 
 import $ from "jquery";
+import Popper from 'popper.js';
+(window as unknown as {Popper:unknown}).Popper = Popper;//XXX: 왜 popper를 이렇게 불러야 하는가?
 import 'bootstrap';
 
 import axios from "axios";