[Devops] Add github action for uploading docker image to dockerhub on merge to develop / master

[aniri]

The image is needed for an easier setup for FE devs.

See https://github.com/code4romania/expert-consultation-api/blob/develop/.github/workflows/build.yml as an example.

[dariuschira]

I would like to work on this if possible.
There's a specific action for build-and-deply to dockerhub which I think can be used: https://docs.github.com/en/free-pro-team@latest/actions/guides/publishing-docker-images
This way you'd need only to set up the triggers and credentials I think.