Add Japanese locale (#6433)

src/node/i18n/index.ts

@@ -2,6 +2,7 @@ import i18next, { init } from "i18next"
 import * as en from "./locales/en.json"
 import * as th from "./locales/th.json"
 import * as zhCn from "./locales/zh-cn.json"
+import * as ja from "./locales/ja.json"
 init({
   lng: "en",
   fallbackLng: "en", // language to use if translations in user language are not available.
@@ -18,6 +19,9 @@ init({
     th: {
       translation: th,
     },
+    ja: {
+      translation: ja,
+    },
   },
 })