Feature/add japanese translation

[moksahero]

Related issues

(put links to related issues here)

Short description and why it's useful

add Japanese translation for strings obtained from the latest code base

Screenshots of visual changes before/after (if there are any)

(if you made any changes in the UI layer please provide before/after screenshots)

Screenshot of passed e2e tests (if you are using our standard setup as a backend)

(run yarn test:e2e and paste the results. If you are not using our standard backend setup or demo.vuestorefront.io you can ommit this step)
I'm using demo.vuestorefront.io but yarn test:e2e is giving me some timeout errors

Upgrade Notes and Changelog

• No upgrade steps required (100% backward compatibility)
• I've updated the Upgrade notes and Changelog on how to port existing VS sites with this new feature

Contribution and currently important rules acceptance

• I read and followed contribution rules
• I read the TypeScript Action Plan and adjusted my PR according to it
• I read about Vue Storefront Modules and I am aware that every new feature should be a module