add ja as a translation

Author: kota113

src/index.tsx

@@ -30,3 +30,4 @@ export { default as el } from './translations/el'
 export { default as ru } from './translations/ru'
 export { default as ro } from './translations/ro'
 export { default as id } from './translations/id'
+export { default as ja } from './translations/ja'