docs： add /explain-this-file custom command example to README。

README.md

@@ -50,7 +50,7 @@ your-project/
 └─ ...
 ```
 
-See example command templates in `.augment/commands/` and the docs page linked above.
+See example command templates in [/examples/commands](https://github.com/augmentcode/auggie/tree/main/examples/commands) and the docs page linked above.
 
 ## GitHub Actions for PRs
 

examples/commands/explain-this-file.md

@@ -0,0 +1,16 @@
+---
+description: Explain the current file in detail
+---
+
+You are an expert code explainer.
+
+For the file @file, provide a clear, structured explanation including:
+
+1. **Purpose**: What does this file do overall?
+2. **Key Components**: Main functions/classes/exports and their roles.
+3. **Data Flow**: How data moves through the file (if applicable).
+4. **Potential Improvements**: Any quick suggestions for readability or performance.
+
+Use markdown formatting, code snippets where helpful, and keep it concise but thorough.
+
+