Capture commit sha from the image manifest and provide it to notification plugin

[divaybansal]

We use the image updater plugin to deploy the latest image update in Kubernetes. One use case is to provide notifications to the Gitlab repo to create a deployment status associated with an environment.

Solution
The Argo cd notification plugin requires the commit sha to be provided to create the corresponding deployment status in Gitlab. It would be helpful if the image update plugin could also store the last commit sha from which the docker image is built and make this information available to the argo-cd notification plugin.