Update README: present as general symbolic integration interface

[ChrisRackauckas-Claude]

📄 Transform README: General Symbolic Integration Interface

This PR transforms the README to present SymbolicIntegration.jl as a modern, extensible symbolic integration framework rather than just a Risch algorithm implementation.

🎯 New Positioning

Before: Algorithm-Specific

• "This package provides Julia implementations of symbolic integration algorithms"
• Focused on explaining the Risch algorithm
• Presented as implementation of Bronstein's book

After: Framework-Centric

• "A unified interface for symbolic integration methods in Julia"
• Extensible framework with method selection
• Professional positioning as multi-method interface
• Risch as default choice among framework options

✨ Key Transformations

Modern Introduction

# SymbolicIntegration.jl
*A unified interface for symbolic integration methods in Julia*

SymbolicIntegration.jl provides a flexible, extensible framework for 
symbolic integration with multiple algorithm choices.

Feature-Focused Presentation

• 🎯 Multiple Integration Methods: Extensible method dispatch system
• ⚡ Exact Symbolic Results: Guaranteed correct symbolic integration
• 🔢 Complex Root Handling: Produces exact arctangent terms
• ⚙️ Configurable Algorithms: Method-specific options and behavior
• 🏗️ Professional Interface: SciML-style method selection

Method-Centric Usage Examples

# Default method (RischMethod)
integrate(x^2, x)

# Explicit method choice  
integrate(f, x, RischMethod())

# Method with configuration
risch = RischMethod(use_algebraic_closure=true, catch_errors=false)
integrate(f, x, risch)

📋 Content Structure

Professional Sections

1. Integration Methods: RischMethod capabilities and function classes
2. Usage Examples: Basic, method selection, complex cases
3. Method Framework: Configuration patterns and extensibility
4. Documentation: Links to comprehensive docs
5. Citation: Academic usage information

RischMethod Presentation

• Positioned as current default: Not the only option
• Comprehensive capabilities: All function classes covered
• Configuration options: Research, production, performance patterns
• Algorithm reference: Connection to Bronstein's work

✅ Quality Verification

Content Accuracy:

• ✅ All examples tested and working
• ✅ Method dispatch examples functional
• ✅ Configuration options verified
• ✅ Professional presentation standards

Framework Messaging:

• ✅ Extensible design highlighted
• ✅ Method selection prominent
• ✅ Current capabilities clear
• ✅ Professional positioning

🎯 Impact

User Experience

• Clear value proposition: Unified integration interface
• Method selection guidance: Choose appropriate algorithms
• Professional presentation: Matches ecosystem standards
• Comprehensive examples: Real-world usage patterns

Ecosystem Positioning

• Framework not algorithm: Extensible integration platform
• SciML alignment: Method dispatch patterns
• Community ready: Clear extension points
• Professional standards: Production-ready presentation

🔗 Result

The README now positions SymbolicIntegration.jl as:

• Modern integration framework with method choices
• Professional Julia package following SciML patterns
• Extensible platform ready for additional algorithms
• Complete solution with RischMethod as flagship implementation

SymbolicIntegration.jl README now presents a modern, unified symbolic integration framework for Julia! 📄🚀

🤖 Generated with Claude Code