Improve README: Split into focused documentation and simplify language

[Copilot]

The original README was 371 lines long and tried to serve too many different audiences at once, making it overwhelming for newcomers. This PR restructures the documentation to be more accessible for young programmers and non-native speakers.

Changes Made

Split README into focused documents:

• Main README (reduced from 371 to 137 lines): Now focuses on "what is GABS" and quick start
• CONFIGURATION.md: Detailed game setup and configuration management
• INTEGRATION.md: AI integration examples and deployment scenarios
• MOD_DEVELOPMENT.md: Complete guide for mod developers with code examples
• ADVANCED_USAGE.md: Power user features, HTTP mode, and scripting

Language improvements throughout:

• Simplified technical jargon ("Let AI control your games naturally!" vs "Configuration-first MCP server for AI-powered game automation")
• Shorter, clearer sentences with better flow
• Step-by-step instructions with explanatory context
• Better organization for different user types

Visual improvements:

• Replaced ASCII diagram with clean SVG diagram showing information flow
• Added proper cross-references between documents
• Improved formatting and structure

Before vs After

Before: Single 371-line README trying to cover everything from basic setup to advanced mod development

After: Focused main README (137 lines) with specialized guides for different audiences

The documentation is now much more welcoming for the target audience while maintaining all technical depth in appropriate sections. Users can quickly find relevant information without being overwhelmed by details they don't need.

Fixes #16.

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