Add contact form app to README

Update the project README to include the Contact Form app in the list of supported Halo AI Agent integrations. This keeps the documentation aligned with the current ecosystem of example apps and integrations.

Author: ruibaby

README.md

@@ -104,6 +104,7 @@ Inspector 的协议版本请选择 `legacy` 或 `auto`。
 - [Docsme 文档管理](https://www.halo.run/store/apps/app-yffxw)：让 AI Agent 管理文档
 - [Image Stream](https://www.halo.run/store/apps/app-JxVVb)：让 AI Agent 在 Unsplash、Pixabay、Pexels 搜索并转存无版权图片
 - [瞬间](https://www.halo.run/store/apps/app-SnwWD)：让 AI Agent 管理瞬间内容
+- [联系表单](https://www.halo.run/store/apps/app-gSebd)：使用 Agent 处理运营数据
 
 ## 许可证