Update README.md

Author: Chasen-Zhang

README.md

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+> [!WARNING]  
+> **Important Notice for Contributors**  
+> If you delete a document, you **must** provide the old URL and the new URL for a 301 redirect to ensure proper navigation. Additionally, please notify @Chasen-Zhang about the change, or you can directly modify the redirect configuration in the file: [docusaurus.config.ts#L210](https://github.com/databendlabs/databend-docs/blob/main/docusaurus.config.ts#L210). Failure to do so may disrupt user access.  
+
 # Databend Docs: Your Contributions Matter
 
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