add German translation

src/components/Footer.tsx

@@ -38,6 +38,9 @@ const Languages = () => {
         <li>
           <a href="/?lng=zh-Hant">繁體中文</a>
         </li>
+        <li>
+          <a href="/?lng=de">Deutsch</a>
+        </li>
       </ul>
     </Pane>
   );

src/util/i18n.ts

@@ -21,6 +21,7 @@ i18n
             ja: TRANSLATION_VERSION,
             'zh-Hans': TRANSLATION_VERSION,
             'zh-Hant': TRANSLATION_VERSION,
+            de: TRANSLATION_VERSION,
           },
         },
       ],