Add comprehensive test system with 71 tests (100% pass rate)

Test Framework:
- Created tests/ directory structure
- Added __init__.py for test package
- Implemented 71 comprehensive tests across 3 test suites

Test Suites:
1. test_config_validation.py (25 tests)
   - Valid/invalid config structure
   - Required fields validation
   - Name format validation
   - URL format validation
   - Selectors validation
   - URL patterns validation
   - Categories validation
   - Rate limit validation (0-10 range)
   - Max pages validation (1-10000 range)
   - Start URLs validation

2. test_scraper_features.py (28 tests)
   - URL validation (include/exclude patterns)
   - Language detection (Python, JavaScript, GDScript, C++, etc.)
   - Pattern extraction from documentation
   - Smart categorization (by URL, title, content)
   - Text cleaning utilities

3. test_integration.py (18 tests)
   - Dry-run mode functionality
   - Config loading and validation
   - Real config files validation (godot, react, vue, django, fastapi, steam)
   - URL processing and normalization
   - Content extraction

Test Runner (run_tests.py):
- Custom colored test runner with ANSI colors
- Detailed test summary with breakdown by category
- Success rate calculation
- Command-line options:
  --suite: Run specific test suite
  --verbose: Show each test name
  --quiet: Minimal output
  --failfast: Stop on first failure
  --list: List all available tests
- Execution time: ~1 second for full suite

Documentation:
- Added comprehensive TESTING.md guide
- Test writing templates
- Best practices
- Coverage information
- Troubleshooting guide

.gitignore:
- Added Python cache files
- Added output directory
- Added IDE and OS files

Test Results:
✅ 71/71 tests passing (100% pass rate)
✅ All existing configs validated
✅ Fast execution (<1 second)
✅ Ready for CI/CD integration

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

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

tests/__init__.py

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+# Test package for Skill Seeker