Add a pull request template

Thank you for stopping by, please provide the following information for your issue:

### Description of problem you are trying to solve

### Data to support this is a problem

### Recommendations

### Next Steps

首先检查仓库中现有的贡献或 GitHub 配置约定，并确认 pull request 模板应放置的位置。完成的标准是存在一个 pull request 模板，并提示贡献者填写问题、支持数据、建议和后续步骤。

由索引模型根据 Issue 内容生成。