docs: translate to Japanese CONTRIBUTING.md (#367)

* docs: translate to Japanese CONTRIBUTING.md

* '[pre-commit.ci 🤖] Apply code format tools to PR'

* Apply suggestions from code review

* Apply suggestions from code review

Co-authored-by: Kozo Nishida <[email protected]>

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Kozo Nishida <[email protected]>

Author: 3 people