Add Japanese translation to multilingual.mdx

[shogohida]

Signed-off-by: Shogo Hida shogo.hida@gmail.com

What does this PR do?

Adds Japanese translation to multilingual.mdx

Fixes #18413

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Who can review?

@omarespejel @sgugger

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.

[shogohida]

I used the formal form to translate because Japanese is normally written in a formal way in docs.

I wrote this memo because one of the requirements was to use an informal tone. #18413 (comment)

[sgugger]

@ArthurZucker can you have a look here? Thanks!

[ArthurZucker]

LGTM in terms of the structure! Thanks a lot for working on this 🚀