Write in README how to push the notifier image to auroradev and auroraprod acrs

[tsundvoll]

Describe the improvement you would like to see
We will not have a dedicated workflow for this, since updates to the image is anticipated to be rearer. Instead, document in the README how to push manually

How will this change existing functionality?
NA

How will this improvement affect the current Threat Model?
NA

[olaals]

I have added that notifier image is pushed automatically.
The dev image tag does not depend on the commit, but is rather a hash based on the files that exist under the workflow-notifier directory.

If there is not changes to any files under the workflow-notifier, the same hash will be generated.

It still pushes the same image to the ACR. If we can find a way to skip this pushing if the image with the tag already exists in the acr it would be a small improvement.

Now it overwrites the image with the same image, which is fine, but not really necessary