update usage of commit

Signed-off-by: Pakin <pakin.t@forth.co.th>

README.md

@@ -103,6 +103,18 @@ pathX2: string
 ...
 ```
 
+Expected result
+
+```
+{"result": "commit hash id"}
+```
+
+Error
+
+```
+{"error": "..."}
+```
+
 Example
 
 ```curl