language code for Japanese is not "jp" but "ja" or "ja-JP"

[manabu-nakamura]

🔤 Polyglot PR

The language code for Japanese is not "jp" but "ja" or "ja-JP."
http://www.lingoes.net/en/translator/langcode.htm

Type of change

• Docs update (changes to the readme or a site page, no code changes)
• Ops wrangling (automation or test improvements)
• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Sweet release (needs a lot of work and effort)
• Something else (explain please)

Checklists

• If modifying code, at least one test has been added to the suite