Provide access to the metadata['image.name'] as a top level output

[jeropaul]

Description

My pipeline pushes code to an ECR repo and in a different job (same ci.yaml) it customises an AWS ECS (farget) task definition.

It would be nice if the image metadata['image.name'] was yanked up to be a top level output as I currently have to create the output using:

    outputs:
        python_worker_image_reference: ${{ fromJSON(steps.build-python-worker-image.outputs.metadata)['image.name'] }}

but in my head I'd love to write this as

    outputs:
        python_worker_image_reference: ${{ steps.build-python-worker-image.outputs.image_name }}