i18n(ja): Add new github-pages.mdx translation

[kpab]

Description (required)

Add Japanese translation for github-pages.mdx deploy guide.

Discord: @github_kpab

Related issues & labels (optional)

• Closes #
• Suggested label: i18n

Please review when you have a chance. Thank you!

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Tracked Files

File	Note
ja/guides/deploy/github.mdx	Localization added, will be marked as complete.

Warnings reference

Icon	Description
🔄️	The source for this localization has been updated since the creation of this pull request, make sure all changes in the source have been applied.

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[jp-knj]

@kpab
Thanks for the contribution!

I left a few comments, but they are just minor tweaks. Please feel free to apply the commit suggestions directly

[kpab]

Thank you for the review! I've applied all suggestions.

[jp-knj]

LGTM, Thanks!

[yanthomasdev]

LGTM! Thanks!