Implement initial version of `BrowserPool` and `PlaywrightCrawler`

- Implement the initial version with basic features.
- Codebase in Crawlee should serve as an inspiration:
  - `BrowserPool`: https://github.com/apify/crawlee/tree/v3.10.1/packages/browser-pool
  - `PlaywrightCrawler`: https://github.com/apify/crawlee/tree/v3.10.1/packages/playwright-crawler
- Update documentation in readme with the new crawler.  