[FEATURE_REQUEST] Check if all images are references only by their sha256 tag

[VedantMahabaleshwarkar]

Description of the problem/feature request
A new optional check to verify if all image references are referenced by their sha256 tags only.

Description of the existing behavior vs. expected behavior
not applicable.

Additional context
For disconnected deployments of kubernetes/openshift, the image references in the YAML files are not the usual tags but instead the sha256 tag. It would be nice to have a check to verify this behavior. Since it is not a very common use-case, the check can be optional. The test itself would be similar to an existing latest-tag check, however the regex would be modified to accept only images using the sha256 tag

[VedantMahabaleshwarkar]

I have the changes ready for this in my fork, I see the help wanted and good first issue labels. I'll go ahead and submit a PR for review by the community!

[VedantMahabaleshwarkar]

PR : #539