docs: Add Gemini API conversion examples and troubleshooting guide

[pratik26x]

📝 Purpose

Enhances documentation to help developers working with AI APIs like Google's Gemini by:

• Adding real-world conversion examples
• Documenting common troubleshooting scenarios
• Improving onboarding experience for API developers

🛠 Changes

✅ Added complete Gemini API conversion example in Node.js
✅ Created troubleshooting table for common errors (e.g., nesting limits)
✅ Improved options documentation with AI-specific recommendations

🔗 Related

• Addresses undocumented needs for AI API conversions (added support for adding description for form-urlencoded #123)
• Supports GSoC 2025 proposal research (goo.gle/deepmind-gsoc)

🧪 Verification

1. Copied example to new project → successfully generated collection
2. Tested troubleshooting solutions against real conversion errors

🌟 For Maintainers

I'd love feedback on:

• Whether to add a Gemini-specific options preset
• How to better organize AI-related documentation

[pratik26x]

@maintainer Could you please review this documentation improvement?
It helps developers working with AI APIs like Gemini.

[pratik26x]

Note: This PR is part of my Google Summer of Code 2025 proposal research.
I'm happy to make any adjustments needed!

[pratik26x]

@maintainers As part of my GSoC 2025 proposal research, I've improved documentation for AI API conversions.
Would you:

• Confirm this documentation direction is valuable?
• Suggest any priority areas for Gemini API support?