feat: Add comprehensive configuration system and examples

Added complete configuration support with multiple formats and examples
to help users easily configure py-wikijs for their projects.

New Features:
- Configuration file templates for ENV, YAML, JSON, and INI formats
- config_helper.py: Universal configuration loader and client factory
  * Auto-detects and loads configs from multiple formats
  * Supports environment variables, YAML, JSON, and INI files
  * Provides create_client_from_config() for easy client creation
  * Validates configuration and provides helpful error messages

Configuration Templates:
- config.env.example: Environment variables (Docker, 12-factor apps)
- config.yaml.example: YAML with multi-environment support
- config.json.example: JSON for programmatic configuration
- config.ini.example: INI for traditional setups

Usage Examples:
- using_env_config.py: Complete example using .env files
- using_yaml_config.py: Complete example using YAML configuration
- using_json_config.py: Complete example using JSON configuration

Documentation:
- docs/CONFIGURATION_GUIDE.md: Comprehensive configuration guide
  * All configuration methods explained
  * Security best practices
  * Environment-specific configurations
  * Troubleshooting guide

Benefits:
✅ Flexible configuration (choose your preferred format)
✅ Keep credentials secure (no hardcoding)
✅ Environment-specific configs (dev/staging/prod)
✅ Docker/container-ready
✅ Full validation and error handling
✅ Comprehensive documentation and examples

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

examples/using_yaml_config.py

@@ -0,0 +1,104 @@
+#!/usr/bin/env python3
+"""Example: Using YAML configuration file with py-wikijs.
+
+This example shows how to use a YAML configuration file to configure
+the WikiJS client.
+
+Prerequisites:
+    pip install pyyaml
+
+Setup:
+    1. Copy config.yaml.example to config.yaml
+    2. Update config.yaml with your Wiki.js credentials
+    3. Run this script
+
+Usage:
+    python using_yaml_config.py
+"""
+
+import sys
+from pathlib import Path
+
+# Add examples directory to path
+sys.path.insert(0, str(Path(__file__).parent))
+
+try:
+    import yaml
+except ImportError:
+    print("❌ PyYAML is required for YAML config files")
+    print("Install with: pip install pyyaml")
+    sys.exit(1)
+
+from config_helper import create_client_from_config, load_config
+
+
+def main():
+    """Main function."""
+    print("=" * 60)
+    print("Using YAML Configuration with py-wikijs")
+    print("=" * 60)
+
+    yaml_file = Path(__file__).parent / "config.yaml"
+
+    if not yaml_file.exists():
+        print(f"\n⚠️  config.yaml not found at {yaml_file}")
+        print("   Copy config.yaml.example to config.yaml and update it")
+        return 1
+
+    try:
+        # Load configuration
+        print("\n📁 Loading configuration from config.yaml...")
+        config = load_config(yaml_file)
+        print("✅ Configuration loaded successfully")
+
+        print(f"\nConfiguration:")
+        print(f"  URL: {config.get('wikijs', {}).get('url')}")
+        print(f"  Auth method: {config.get('wikijs', {}).get('auth', {}).get('method')}")
+        print(f"  Timeout: {config.get('client', {}).get('timeout')}s")
+        print(f"  Rate limit: {config.get('client', {}).get('rate_limit')} req/s")
+        print(f"  Log level: {config.get('logging', {}).get('level')}")
+
+        # Create client with environment-specific config
+        env = config.get("environments", {}).get("development", {})
+        if env:
+            print(f"\n🔧 Using development environment settings")
+
+        print("\n🔌 Creating WikiJS client...")
+        client = create_client_from_config(config)
+        print(f"✅ Client created successfully")
+
+        # Test connection
+        print("\n🔍 Testing connection...")
+        pages = client.pages.list()
+        print(f"✅ Connected! Found {len(pages)} page(s)")
+
+        if pages:
+            print(f"\n📄 Sample pages:")
+            for page in pages[:3]:  # Show first 3
+                print(f"   - [{page.id}] {page.title} ({page.path})")
+
+        # Show metrics
+        metrics = client.get_metrics()
+        print(f"\n📊 Client Metrics:")
+        print(f"   Total requests: {metrics['total_requests']}")
+        print(f"   Error rate: {metrics.get('error_rate', 0):.2f}%")
+
+    except FileNotFoundError as e:
+        print(f"❌ {e}")
+        return 1
+
+    except Exception as e:
+        print(f"❌ Error: {e}")
+        import traceback
+
+        traceback.print_exc()
+        return 1
+
+    print("\n" + "=" * 60)
+    print("✅ Example completed successfully!")
+    print("=" * 60)
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())