Allow for disabling force push

If the action is pushing to the same branch, it is likely desirable to
do a regular push instead of a force which might overwrite other
changes in case the source has changed after the action triggered.

To not break the interface of the action, add a boolean flag to turn
on 'NO_FORCE_PUSH' mode.

entrypoint.sh

@@ -37,8 +37,14 @@ git add . && \
 git status && \
 curr_branch="$(git rev-parse --abbrev-ref HEAD)" && \
 commit_msg="${COMMIT_MSG:-'Marp Action Build'}" && \
-git commit -m "${commit_msg}" && \
-git push --force $remote_repo ${curr_branch}:${PUBLISH_TO_BRANCH}
+git commit -m "${commit_msg}" 
+
+if [ "$NO_FORCE_PUSH" = true ]
+then 
+  git push $remote_repo ${curr_branch}:${PUBLISH_TO_BRANCH}
+else
+  git push --force $remote_repo ${curr_branch}:${PUBLISH_TO_BRANCH}
+fi
 
 echo "✔  Pushed Successfully!"
 echo ""