Add Redirect Checker to Testing tools section

[brancogao]

Summary

Added Redirect Checker to the Testing tools and frameworks section under API Testing.

Details

• Redirect Checker - An HTTP redirect chain analyzer for testing redirect configurations, detecting loops, and measuring response times
• GitHub: https://github.com/brancogao/redirect-checker
• Demo: https://redirect-checker.autocompany.workers.dev

This tool is useful for:

• Testing URL redirect configurations
• Detecting redirect loops
• Verifying SEO-critical 301/302 redirects
• Measuring redirect chain performance

Checklist

• The title follows the existing format
• The entry is placed in the appropriate section