Document Docker CI bucket output

Add the Docker workflow artifact path to the public CI bucket layout.

README.md

@@ -131,6 +131,7 @@ The bucket uses the following layout:
 ```text
 github_actions/
 ├── boost/predicted_labels/
+├── docker/saved_model/
 ├── prediction/predicted_labels/
 ├── train/saved_model/
 └── tta/predicted_labels/