feat: add Japanese language support to language (#50)

* Add Japanese language support to language names

* Add files via upload

* Update missing body text in ja_JP.json

* Update GDK missing title message in Japanese

* Update check_unused_keys.py

* Update remove_unused_keys.py

* Update i18n.ts

* Fix translation reference for Japanese language

* Add Japanese language support in OnboardingPage

* Update SettingsPage.tsx

* Update i18n.ts

* Update i18n.ts

* Fix formatting of Russian language entry

Author: kazaminosuke