Add Clarvia AEO badge — agent-readiness score for HuggingChat

[digitamaz]

Hi HuggingFace team! 👋

Clarvia benchmarks 27,900+ AI tools using AEO (Agent Engine Optimization) scores — a quality signal for AI agent integration.

HuggingChat/chat-ui is an increasingly important platform for AI agents and tool use. An AEO badge would signal to developers that the chat-ui integrates well with the agent ecosystem:

[![AEO Score](https://clarvia.art/api/badge/huggingface/chat-ui)](https://clarvia.art)

Would you be open to adding this to the README? 🤗