Update README to highlight comprehensive IntelliSense documentation

Added section noting that all public APIs now include comprehensive
XML documentation with IntelliSense support.

Users can now discover:
- Method descriptions with Gotenberg documentation links
- Parameter explanations and valid ranges
- Exception handling guidance
- Usage notes and best practices

This completes Phase 9 and the entire documentation improvement initiative.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: Jaben

README.md

@@ -40,6 +40,13 @@ PM> Install-Package Gotenberg.Sharp.Api.Client
 
 *Note: Use v1.x nugets for Gotenberg v6.*
 
+## IntelliSense Documentation
+All public APIs include comprehensive XML documentation with clear descriptions, parameter details, and links to official Gotenberg documentation. IntelliSense provides:
+- Method descriptions with Gotenberg route documentation links
+- Parameter explanations and valid value ranges
+- Exception documentation for error handling
+- Usage notes and best practices
+
 ## AppSettings
 ```json
   "GotenbergSharpClient": {