Enhance Markdown generation and external content control

- Integrate customized html2text library for flexible Markdown output
- Add options to exclude external links and images
- Improve content scraping efficiency and error handling
- Update AsyncPlaywrightCrawlerStrategy for faster closing
- Enhance CosineStrategy with generic embedding model loading

crawl4ai/html2text/__main__.py

@@ -0,0 +1,3 @@
+from .cli import main
+
+main()