docs: Update README.ja-JP.md

[kaitas]

Happy to contribute here!

[comfyui-wiki]

For me, the main thing I'm considering right now is that I don't know Japanese. And since our updates are very frequent, it might be hard for the community to contribute content to keep it updated synchronously.

So I'm wondering if we need to add Japanese support to the docs.

I use AI to help translate content on my site comyui-wiki.com, but I still do it manually every time. I know syncing multilingual content takes a lot of time, and it also makes team members spend more time updating the docs.

[comfyui-wiki]

Let me sync with the team member later. And thank you for contributing to our docs 🩷