Provide Docker image via registry

[dedo1911]

As of #153 the docker image is being provided via Github Release Page, which is not optimal

Previous mssql-tools are correctly released: https://hub.docker.com/r/microsoft/mssql-tools

New go-sqlcmd docker image is expected to be correctly tagged on a registry, being it Dockerhub or Microsoft's own MCR https://mcr.microsoft.com

Current workaround provided by third-party: https://github.com/fabiang/docker-sqlcmd