feat(crawler): add session management and view-source support

Add session_id feature to allow reusing browser pages across multiple crawls.
Add support for view-source: protocol in URL handling.
Fix browser config reference and string formatting issues.
Update examples to demonstrate new session management features.

BREAKING CHANGE: Browser page handling now persists when using session_id

docs/examples/hello_world.py

@@ -8,17 +8,19 @@ from crawl4ai import (
     CrawlResult
 )
 
-                   
 
-async def main():    
-    browser_config = BrowserConfig(headless=True, verbose=True)
+async def main():
+    browser_config = BrowserConfig(
+        headless=False,
+        verbose=True,
+    )
     async with AsyncWebCrawler(config=browser_config) as crawler:
         crawler_config = CrawlerRunConfig(
             markdown_generator=DefaultMarkdownGenerator(
                 content_filter=PruningContentFilter()
             ),
         )
-        result : CrawlResult = await crawler.arun(
+        result: CrawlResult = await crawler.arun(
             url="https://www.helloworld.org", config=crawler_config
         )
         print(result.markdown.raw_markdown[:500])