Add API Documentation

[devin-ai-integration]

Create comprehensive API documentation covering:

• Core functions and classes
• Parameters and return types
• Usage examples
• Error handling

Example additions:

## API Reference
### get_sage(provider, model, base_url=None, api_key=None, mode='default')
Creates a new ShellSage instance with specified configuration.

Parameters:
- provider: str - The AI provider to use ('anthropic' or 'openai')
- model: str - Model name to use

Estimated time: 3-4 hours

[ryan-m-pearson]

Hi, I'd love to try and tackle this. I'm a tech writer looking to break into the API docs space and I'd love to contribute! Let me know!

[Den4ikGyl]

Hi, I'd love to try and tackle this. I'm a tech writer looking to break into the API docs space and I'd love to contribute! Let me know!

[Garrett-star]

Hello, do you need a help with api documentation?