This PR adds thorough documentation for the SpriteAI module, providing developers with detailed information about its functionality and usage.

Key additions include:

• Complete API reference for all core functions
• Installation instructions and dependencies
• Detailed parameter descriptions and return values
• Usage examples for each function
• Clear documentation structure with table of contents
• Helper function documentation
• Implementation notes and requirements

The documentation covers:

• Character spritesheet generation
• Environment sprite generation
• Item sprite generation
• Animation state management
• Sprite style configuration
• Background removal utilities

This documentation will help developers:

• Understand the full capabilities of the SpriteAI module
• Properly implement sprite generation features
• Configure sprite generation parameters
• Handle the various output formats and options

Location: docs/spriteai/index-js-documentation.md