feat(content-filter): add LLMContentFilter for intelligent markdown generation

Add new LLMContentFilter class that uses LLMs to generate high-quality markdown content:
- Implement intelligent content filtering with customizable instructions
- Add chunk processing for handling large documents
- Support parallel processing of content chunks
- Include caching mechanism for filtered results
- Add usage tracking and statistics
- Update documentation with examples and use cases

Also includes minor changes:
- Disable Pydantic warnings in __init__.py
- Add new prompt template for content filtering

crawl4ai/__init__.py

@@ -76,3 +76,10 @@ else:
     WebCrawler = None
     # import warnings
     # print("Warning: Synchronous WebCrawler is not available. Install crawl4ai[sync] for synchronous support. However, please note that the synchronous version will be deprecated soon.")
+
+import warnings
+from pydantic import warnings as pydantic_warnings
+
+# Disable all Pydantic warnings
+warnings.filterwarnings("ignore", module="pydantic")
+# pydantic_warnings.filter_warnings()