[FEATURE] imagePullSecrets

Hello everybody This is a feature request.

Can you guys add imagePullSecrets to the Helm charts?

My company has its registry, and we want to store the StackGres images on our registry.

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I know there is imagePullSecrets, but it's not very well documented.

I think it's kind of confusing that put its value under serviceAccount.repoCredentials.

Also, I think values for image should change

from:

"{{ .Values.operator.image.name }}:{{ .Values.operator.image.tag }}"

to:

"{{ .Values.containerRegistry }}/{{ .Values.operator.image.name }}:{{ .Values.operator.image.tag }}"