Add release based containers

[syeopite]

• Changes the current master based container to use "master" tag instead of "latest" tag
• Adds a new workflow to build a container on each new release which has the "latest" tag, and a tag based on the current released version.

Once this process is done, it should allow us to quickly merge PRs which passed the code-review but not the testing stage. Instead, the testing-stage can be pushed to when each release occurs.