feat: add option of ja

Refs #149

quiz-app/src/App.vue

@@ -7,6 +7,7 @@
         <option>en</option>
         <option>tr</option>
         <option>fr</option>
+        <option>ja</option>
       </select>
     </nav>
     <div id="app">

quiz-app/src/assets/translations/index.js

@@ -2,13 +2,15 @@
 import en from './en.json';
 import tr from './tr.json';
 import fr from './fr.json';
+import ja from './ja.json';
 
 //export const defaultLocale = 'en';
 
 const messages = {
 	en: en[0],
 	tr: tr[0],
-	fr: fr[0]
+	fr: fr[0],
+	ja: ja[0]
 };
 
 export default messages;