(WIP) 로그인 컴포넌트 구현

+import React, { useContext, useState } from 'react';
+import { RouteComponentProps } from 'react-router';
+import SocketContext from './SocketContext';
+
+export const Login: React.FC<RouteComponentProps> = ({ history }) => {
+    const socket = useContext(SocketContext);
+    const [ username, setUsername ] = useState("");
+
+    const login = () => {
+      socket.emit('LoginMessage', username, ({ ok } : { ok: boolean }) => {
+        if (ok) {
+          history.push('/rooms');
+        } else {
+          console.error('login error!'); // TODO: 팝업 에러?
+        }
+      });
+    }
+
+    return (
+      <div>
+        <header>Header</header>
+        <div className="flex items-center">
+          <input type="text"
+              placeholder="Username"
+              className="px-3 py-2 bg-white
+                  placeholder-gray-300 text-gray-700 text-sm
+                  rounded shadow outline-none focus:outline-none"
+              value={username}
+              onChange={e => setUsername(e.target.value)}
+          />
+          <button className="bg-green-500 active:bg-green-600
+                          text-white font-bold uppercase text-sm
+                          px-5 py-2 ml-3 rounded shadow hover:shadow-lg
+                          outline-none focus:outline-none
+                          ease-linear transition-all duration-150"
+                  type="button"
+                  onClick={() => login()}>Login</button>
+        </div>
+        <footer>Footer</footer>
+      </div>
+    )
+}