[v0.3.71] Enhance chunking strategies and improve overall performance

- Add OverlappingWindowChunking and improve SlidingWindowChunking
- Update CHUNK_TOKEN_THRESHOLD to 2048 tokens
- Optimize AsyncPlaywrightCrawlerStrategy close method
- Enhance flexibility in CosineStrategy with generic embedding model loading
- Improve JSON-based extraction strategies
- Add knowledge graph generation example

crawl4ai/async_crawler_strategy.py

@@ -134,7 +134,7 @@ class AsyncPlaywrightCrawlerStrategy(AsyncCrawlerStrategy):
 
     async def close(self):
         if self.sleep_on_close:
-            await asyncio.sleep(500)
+            await asyncio.sleep(0.5)
         if self.browser:
             await self.browser.close()
             self.browser = None