docs: add Japanese README file

[eltociear]

I created Japanese translated README.

[Hisoka-X]

Thanks for your contribution, but I think Japanese documentation is not very meaningful for seatunnel at this stage. No one can maintain it.

[Stardust002]

Thanks for your contribution, but I think Japanese documentation is not very meaningful for seatunnel at this stage. No one can maintain it.

hi, there is a problem when I build the program, I saved the error message like this, maybe the sidebar.js is missing, waht should I do? looking forward to your reply,thanks

[Hisoka-X]

@Stardust002 try npm run sync before first build.