Merge pull request 'cleanup' (#4) from v1_clean-up into v1_main

Reviewed-on: #4

action.sh

@@ -11,3 +11,5 @@ echo "run docker build"
 docker build -t ${INPUT_CONTAINER_DOMAIN,,}/${INPUT_CONTAINER_NAME,,}:${INPUT_CONTAINER_TAG,,} --no-cache .
 echo "run docker push"
 docker push $INPUT_CONTAINER_DOMAIN/$INPUT_CONTAINER_NAME:$INPUT_CONTAINER_TAG
+echo "run docker prune"
+docker system prune -a -f