Refactor: Internationalize comments and test data in write demo package

[X-qinghai]

Purpose of the pull request

This pull request addresses the internationalization (i18n) of the fesod-sheet-examples module. It translates legacy Chinese comments, Javadocs, and string literals (such as Excel headers and sheet names) into English within the write demo package.

This ensures the codebase aligns with the Apache Software Foundation's "English First" policy and makes the examples accessible to the global developer community.

What's changed?

I have translated the contents of the org.apache.fesod.sheet.demo.write package from Chinese to English, covering:

1. Test Class (WriteTest.java):

   • Translated all Javadocs and inline comments explaining the writing strategies.
   • Renamed hardcoded Chinese strings (e.g., changed sheet name "模板" to "Template").
   • Translated test data generation strings.

2. Data Classes (POJOs):

   • Updated @ExcelProperty annotations to use English headers (e.g., ColorDemoData, ComplexHeadData, ConverterData, etc.).
   • Translated field comments and class descriptions.

3. Handlers:

   • Translated logging messages and comments in custom write handlers (CommentWriteHandler, CustomCellWriteHandler, etc.).

No logic changes were made; this is purely a documentation and string literal refactoring.

Checklist

• I have read the Contributor Guide.
• I have written the necessary doc or comment.
• I have added the necessary unit tests and all cases have passed.

[delei]

Since the Maven module has been changed, please resolve the conflicts first :)