📚 Expand README with comprehensive error handling patterns

[mj-muin]

Overview

Adds comprehensive real-world error handling patterns and examples to help developers avoid common pitfalls and implement proper error handling.

Changes

• ✅ 7 error handling patterns with detailed explanations
• ✅ Pattern 1: Promise rejection handling (unhandled rejections)
• ✅ Pattern 2: Try-catch anti-patterns and defensive programming
• ✅ Pattern 3: Async error propagation in Express
• ✅ Pattern 4: Event emitter error handling
• ✅ Pattern 5: Callback error handling for legacy code
• ✅ Pattern 6: Error context and stack traces
• ✅ Pattern 7: Timeout and resource cleanup

Statistics

• Lines added: 769
• New sections: Error Handling Patterns
• Examples: 7 complete patterns with code

Links to new sections

• Error Handling Patterns
  • Unhandled Promise Rejections
  • Try-Catch Anti-Patterns
  • Async Error Propagation
  • Event Emitter Errors
  • Callback Error Handling
  • Error Context & Stack Traces
  • Timeout & Resource Cleanup

Why this matters

• Helps developers avoid common error handling mistakes
• Provides copy-pasteable, production-ready patterns
• Reduces debugging time significantly
• Improves code reliability and maintainability