Add weather agent example

[athika2225-wq]

Summary

Added a new weather_agent example that fetches live weather information for user-provided cities using the OpenWeather API.
Features included:

• Live weather lookup
• Error handling for invalid city names
• README documentation
• Demo screenshots

Type of Change

• New agent example
• Documentation update

Checklist

• I have starred this repository.
• I added/updated README.md for changed example(s).
• I added demo image/GIF (if applicable).
• I updated CHANGELOG.md (required for non-doc changes).
• I verified paths/commands used in docs.

Related Issue

None

Notes for Reviewers

The agent was tested locally with multiple city queries and invalid city handling.

[gautammanak1]

Thanks for the contribution 🚀

One important suggestion: please use the Agent Chat Protocol (uagents_core.contrib.protocols.chat — ChatMessage / chat_protocol_spec) for agent communication, instead of custom message models. This keeps the example aligned with the rest of the repo and makes the agent discoverable + chat-compatible on Agentverse/ASI:One.

You can reference how the other examples wire it up via their chat_proto.py. Once Chat Protocol support is added (and CI is green), this will be ready for review. Let me know if you need any help! 🙌