remove docs

.drone.yml

   - echo "copy docs to ${DRONE_REPO_NAME}"; cp -r ../docs/* .
   - ls
   - echo "add files in ${DRONE_REPO_NAME}"; git add -A
-  - git commit -m "Drone tagged as ${DRONE_TAG}"
+  - git commit --allow-empty -m "Drone tagged as ${DRONE_TAG}"
   - git push --force origin master
   environment:
     GIT_USER: