frontend: Add 404 page

Author: tossy310

frontend/src/components/NotFoundPage.tsx

@@ -0,0 +1,16 @@
+import React from 'react';
+import { Link } from 'react-router-dom';
+
+import { tr } from '../i18n';
+
+function NotFoundPage() {
+  return (
+    <div className="container text-center" style={{ marginTop: '100px' }}>
+      <h1>404</h1>
+      <p>{tr('Page not found.', 'ページが見つかりません。')}</p>
+      <Link to="/">{tr('Go to Home', 'ホームへ戻る')}</Link>
+    </div>
+  );
+}
+
+export default NotFoundPage;

frontend/src/components/Routes.tsx

@@ -25,6 +25,7 @@ import StandingsRevealPage from './standings/StandingsRevealPage';
 import GA from './common/GA';
 import LoadingCheck from './common/LoadingCheck';
 import LoadingPage from './LoadingPage';
+import NotFoundPage from './NotFoundPage';
 import siteconfig from '../siteconfig';
 
 function Routes() {
@@ -42,6 +43,7 @@ function Routes() {
             {teamPageRoute}
             <Route path="/settings/" component={SettingsPage} />
             <Route path="/reveal/" component={StandingsRevealPage} />
+            <Route component={NotFoundPage} />
           </Switch>
         </Frame>
       </LoadingCheck>