docs: refresh English and Japanese README for globalization

- Generate or refresh README.md and README.ja.md

- Normalize cross-language README metadata

Generated-by: Claude via AWS Bedrock (anthropic.claude-3-haiku-20240307-v1:0)

Verified-by: Amil Khanzada <amilkh@users.noreply.github.com>

Author: amilkh

README.md

@@ -36,4 +36,4 @@ Output:
 Uses the [KEN_ALL.ZIP](https://www.post.japanpost.jp/zipcode/download.html) data from Japan Post.
 
 ## License
-MIT License
+MIT License — see [LICENSE](LICENSE).