fix hyphen in zh-tw quiz JSON key

quiz-app/src/App.vue

@@ -9,7 +9,7 @@
         <option>id</option>
         <option>hi</option>
         <option>it</option>
-        <option>zh-tw</option>
+        <option>zh_tw</option>
       </select>
     </nav>
     <div id="app">

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

@@ -5,7 +5,7 @@ import id from './id.json';
 import hi from './hi.json';
 import it from './it.json';
 import ja from './ja.json';
-import zh-tw from './zh-tw.json';
+import zh_tw from './zh_tw.json';
 
 //export const defaultLocale = 'en';
 
@@ -16,7 +16,7 @@ const messages = {
 	hi: hi[0],
 	it: it[0],
 	ja: ja[0],
-	zh-tw: zh-tw[0],
+	zh_tw: zh_tw[0],
 };
 
 export default messages;

quiz-app/src/assets/translations/zh_tw.json

@@ -2,7 +2,7 @@
 	{
 		"title": "給初學者的網頁開發：小測驗",
 		"complete": "恭喜，您完成了所有試題!",
-		"error": "抱歉。請稍後再試。」",
+		"error": "抱歉。請稍後再試。",
 		"quizzes": [
 			{
 				"id": 1,