Adds a new BrowserManager implementation with browser pooling and page pre-warming capabilities:
- Adds support for managing multiple browser instances per configuration
- Implements page pre-warming for improved performance
- Adds configurable behavior for when no browsers are available
- Includes comprehensive status reporting and monitoring
- Maintains backward compatibility with existing API
- Adds demo script showcasing new features
BREAKING CHANGE: BrowserManager API now returns a strategy instance along with page and context