test: 添加测试文件用于PR演示

[1982189190-commits]

变更内容

• 添加了一个测试文件 test.md，用于演示完整的 PR 提交流程。

目的

此 PR 用于测试和熟悉 Apache Doris 的贡献流程，不涉及功能性变更。

[hello-stephen]

Thank you for your contribution to Apache Doris.
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Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
3. What features were added. Why was this function added?
4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?