Add Agentset

[Enes830]

This PR adds Agentset to the Tools section.

Agentset is an open-source platform for building production-ready RAG applications with built-in agentic reasoning, hybrid search, and multimodal support.

Why it fits:

• Similar to existing tools like LlamaIndex, Verba, NEUM, and Kiln in this section
• Open-source RAG platform with production focus
• Actively maintained

Checklist:

• Follows the existing format: Name, Description, Website/GitHub links
• Added to Tools section
• Description is concise