ci: Deploy docker image to DockerHub

[VikashKothary]

See: #152

[update-freak]

When will the docker will be deploayed to DockerHub?
From what I saw the version in dockerHub is quite old.

[VikashKothary]

Currently, the docker image for this repo is deployed to DockerHub from this repository: https://github.com/ankicommunity/anki-devops-services.

But it is likely that is be combined into this repo since the maintainer for that repo has since left and it'll be easier for me to maintain one repo.

In terms of timelines, I always welcome community contributions. The limited time I have will most likely be focused around this issue: #158. So can't say anything more concrete for now.