Created automated workflow for Docker image build on DockerHub

[zeppelinux]

Can't create PR for this repo, had to clone to https://github.com/zeppelinux/ninjam
It builds, creates the release and activates the DockerHub image build

https://hub.docker.com/r/zeppelinux/ninjam-server

Planning to make the Helm Charts for K8's deployment

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