docs(customize): add note about default prompt location #256

Added a note in the customization documentation to indicate the location of default prompt files in `src/main/resources/genius/` and provided a link for reference.

Author: phodal

docs/customize/prompt-override.md

@@ -46,3 +46,7 @@ For example, create a file named `prompts/sql/sql-gen-clarify.vm`, will override
 └── sre
     └── generate-dockerfile.vm
 ```
+
+系统自带的 Prompt 文件在 `src/main/resources/genius/` 目录下，可以参考这些文件进行自定义（保持变量名一致）。
+
+详细见：https://github.com/unit-mesh/auto-dev/tree/master/core/src/main/resources/genius