Improve Language Support Documentation and Implementation

[Cfomodz]

This PR improves the language support by updating documentation, language codes, and examples to match Kokoro-TTS v0.23.

Changes

Language Support Updates

• Updated language codes to match Kokoro-TTS v0.23:
  • Japanese: "ja" → "ja-jp"
  • Korean: "ko" → "ko-kr"
  • Chinese: "cmn" → "zh-cn"

Documentation Improvements

1. Added comprehensive language support documentation in:

   • Class docstrings
   • Method docstrings
   • README.md
   • Example files

2. Added clear warnings and notes about CJK language limitations:

   • English letters not properly handled by tokenizers
   • Recommendations for handling English text in CJK languages

Example Improvements

• Updated examples/languages.py with:
  • Better test sentences for each language
  • Error handling and feedback
  • Clear documentation and usage instructions
  • Language-specific comments and best practices

Code Quality

• Added detailed docstrings to Kokoro class and methods
• Improved error messages for language code validation
• Added return type documentation

Testing

The changes can be tested by running the improved language example:

python examples/languages.py

Issues
Closes #6 - Support all 5 languages