feat(content): add target_elements parameter for selective content extraction

Adds new target_elements parameter to CrawlerRunConfig that allows more flexible content selection than css_selector. This enables focusing markdown generation and data extraction on specific elements while still processing the entire page for links and media.

Key changes:
- Added target_elements list parameter to CrawlerRunConfig
- Modified WebScrapingStrategy and LXMLWebScrapingStrategy to handle target_elements
- Updated documentation with examples and comparison between css_selector and target_elements
- Fixed table extraction in content_scraping_strategy.py

BREAKING CHANGE: Table extraction logic has been modified to better handle thead/tbody structures

crawl4ai/async_webcrawler.py

@@ -514,7 +514,8 @@ class AsyncWebCrawler:
                 scraping_strategy.logger = self.logger
 
             # Process HTML content
-            params = {k: v for k, v in config.to_dict().items() if k not in ["url"]}
+            params = config.__dict__.copy()
+            params.pop("url", None)            
             # add keys from kwargs to params that doesn't exist in params
             params.update({k: v for k, v in kwargs.items() if k not in params.keys()})