Add option of saving docker image to the artifact storage optional

[nils1k]

Is your feature request related to a problem? Please describe.
We build our application using a multi-stage Docker build and have a single workflow where we build the docker image and then scan it using gha-docker. However, this approach takes up an unnecessary amount of space in the Github Actions artifact storage as we run our workflow on both push and pull request when publishing the image to the storage and scanning it for vulnerabilities is really only necessary for pull request and main builds.

Describe the solution you'd like
I want to be able to choose whether or not to publish the docker image to the Github Actions artifact storage through an input parameter.

Describe alternatives you've considered
N/A

Additional context
N/A

[Glenn-Terjesen]

@nils1k take a look at entur/platform-examples where we build the image just once.
Artifact storage is needed by the docker scan and ++ logic..