[Feature]: 希望学术检索助手增加对pubmed的支持

### Class | 类型

函数插件

### Feature Request | 功能请求

[pubmed](https://pubmed.ncbi.nlm.nih.gov/)有大量的医学文献，希望学术检索助手增加对pubmed的支持，对医学相关的人员很有帮助，感谢🙏

The issue names no implementation file, test, or entry point. Start by reviewing the repository's function-plugin structure and the PubMed site linked in the request; done would mean adding PubMed support for academic retrieval, but the expected behavior and acceptance criteria need clarification.

Written by the indexing model from the issue text.