docs(api): add streaming mode documentation and examples

Add comprehensive documentation for the new streaming mode feature in arun_many():
- Update arun_many() API docs to reflect streaming return type
- Add streaming examples in quickstart and multi-url guides
- Document stream parameter in configuration classes
- Add clone() helper method documentation for configs

This change improves documentation for processing large numbers of URLs efficiently.

docs/md_v2/core/quickstart.md

@@ -265,9 +265,21 @@ async def quick_parallel_example():
         "https://example.com/page3"
     ]
     
-    run_conf = CrawlerRunConfig(cache_mode=CacheMode.BYPASS)
+    run_conf = CrawlerRunConfig(
+        cache_mode=CacheMode.BYPASS,
+        stream=True  # Enable streaming mode
+    )
 
     async with AsyncWebCrawler() as crawler:
+        # Stream results as they complete
+        async for result in await crawler.arun_many(urls, config=run_conf):
+            if result.success:
+                print(f"[OK] {result.url}, length: {len(result.markdown_v2.raw_markdown)}")
+            else:
+                print(f"[ERROR] {result.url} => {result.error_message}")
+
+        # Or get all results at once (default behavior)
+        run_conf = run_conf.clone(stream=False)
         results = await crawler.arun_many(urls, config=run_conf)
         for res in results:
             if res.success:
@@ -279,8 +291,13 @@ if __name__ == "__main__":
     asyncio.run(quick_parallel_example())
 ```
 
+The example above shows two ways to handle multiple URLs:
+1. **Streaming mode** (`stream=True`): Process results as they become available using `async for`
+2. **Batch mode** (`stream=False`): Wait for all results to complete
+
 For more advanced concurrency (e.g., a **semaphore-based** approach, **adaptive memory usage throttling**, or customized rate limiting), see [Advanced Multi-URL Crawling](../advanced/multi-url-crawling.md).
 
+---
 
 ## 8. Dynamic Content Example