docs: improve README with comprehensive guide and examples

[ARUSHIGULBHILE]

This PR significantly improves the Playwright Python README by:

• Adding clear step-by-step installation instructions
• Including complete working examples for beginners
• Adding troubleshooting section for common issues
• Organizing content with better sections and formatting
• Explaining key features and use cases clearly
• Adding comprehensive contributing guidelines

These enhancements will help new users get started with Playwright Python more easily.