docs: add Japanese translation for bubble sort

[KoHaRxnP]

Description

This PR adds a Japanese translation for the Bubble Sort explanation.
It aims to help Japanese-speaking learners understand the algorithm better.

• Created ja/ソートアルゴリズム/バブルソート.md
• Followed the structure of the original English documentation.

Checklist

• [ x ] A description of the changes in this PR is mentioned above.
• [ x ] All the new and existing checks pass.
• [ x ] No plagiarized, duplicated, or repetitive documentation that has been directly copied from another source.
• [ x ] If it's a new explanation, it contains solid, understandable, and accessible information.
• [ x ] I have read the whole contributing guidelines and agree to the Code of Conduct.

Note to reviewers

Added Japanese translation for bubble sort documentation.

[KoHaRxnP]

That sounds a bit unnatural