Add Japanese translations

[kota113]

Thank you for creating this library!
As a developer from Japan, I'd like to add Japanese translations to it.

* I haven't checked the translation yet. I still need to check whether the translation is appropriate for the usage.

[iM-GeeKy]

@kota113 Here is a another translation PR as a reference. Make sure to add ja to the docusaurus and example directory files respectively. Thanks for the pull request though!

[kota113]

Thanks!! I'll follow the procedure and add "ja" to them.

[iM-GeeKy]

@kota113 Could you update the App.tsx to include ja? Take a look at this for reference.

[kota113]

It took a while but completed!
I was a bit busy and couldn't take a time to do this. sry :)