Update creating-a-docker-container-action.md

[arivictor]

Why:

Despite following all the steps as per this guide, I encountered the below issue when testing my action:

docker: Error response from daemon: failed to create task for container: failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: exec: "/entrypoint.sh": permission denied: unknown.

What's being changed (if available, include any code snippets, screenshots, or gifs):

Include a step in the example Dockerfile to make the entrypoint.sh executable in the container. Once I had added this my action worked without issue.

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