docs: update usage with correct link to action

Author: kceb

README.md

@@ -17,12 +17,12 @@ The git-message
 ## Example usage
 Without SHA:
 ```
-uses: actions/git-message-action@v1
+uses: kceb/git-message-action@v1
 ```
 
 With specified SHA:
 ```
-uses: actions/git-message-action@v1
+uses: kceb/git-message-action@v1
 with:
   sha: '2905893ab6e5f2644201c2abc04e3d83bf317d9b'
 ```