[Translations] Japanese ja_JP - Chapter 1

[nwiizo]

Description: Resolves #61 /kind documentation

This PR adds the Japanese translation for Chapter 1 of the "Platforms on Top of Kubernetes" book.

Changes include:

• Added README-ja.md containing the Japanese translation of Chapter 1
• Updated the "Available in" section in README.md to include a link to the Japanese translation
• Ensured consistency in formatting and structure with other translation files

As a native Japanese speaker with a keen interest in Kubernetes and cloud-native technologies, I believe this translation will help make the valuable content in this book more accessible to the Japanese-speaking community.

Please review the translation and provide any feedback or suggestions for improvement. I'm open to making further changes to ensure the highest quality of the translated content.

Thank you for considering this contribution to the project!

Kind regards,

[salaboy]

I am sure that this translation will help the Japanese speaking community a lot! I hope the book also gets translated to Japanese

[salaboy]

thanks so much for this PR! merging as it looks great!