Update and fix ja translation

index.html

@@ -146,6 +146,7 @@
 
         <script src='locale/locale.js'></script>
         <script src='locale/en.js'></script>
+        <script src='locale/ja.js'></script>
         <script src='locale/fr.js'></script>
         <script src='locale/de.js'></script>
         <script src='locale/lv.js'></script>

locale/ja.js

@@ -1,4 +1,4 @@
-locale.en = {
+locale.ja = {
     modes: {
         add_area: {
             title: "エリア",