chore: Add Community Events section to README

This change adds a new section to the README.md, detailing past community events. The first entry is for the completed ADK's 1st community meeting, with links to the recording and deck.

PiperOrigin-RevId: 823322924

Author: hangfei

README.md

@@ -155,6 +155,10 @@ We welcome contributions from the community! Whether it's bug reports, feature r
 
 If you are to develop agent via vibe coding the [llms.txt](./llms.txt) and the [llms-full.txt](./llms-full.txt) can be used as context to LLM. While the former one is a summarized one and the later one has the full information in case your LLM has big enough context window.
 
+## Community Events
+
+- [Completed] ADK's 1st community meeting on Wednesday, October 15, 2025. Remember to [join our group](https://groups.google.com/g/adk-community) to get access to the [recording](https://drive.google.com/file/d/1rpXDq5NSH8-MyMeYI6_5pZ3Lhn0X9BQf/view), and [deck](https://docs.google.com/presentation/d/1_b8LG4xaiadbUUDzyNiapSFyxanc9ZgFdw7JQ6zmZ9Q/edit?slide=id.g384e60cdaca_0_658&resourcekey=0-tjFFv0VBQhpXBPCkZr0NOg#slide=id.g384e60cdaca_0_658).
+
 ## 📄 License
 
 This project is licensed under the Apache 2.0 License - see the [LICENSE](LICENSE) file for details.