added imagepullsecrets to service accounts in helm chart

[Alex2357]

Background

Added ability to add imagePullSecrets for service accounts if requried to specify it

Testing Procedure

• Test as tested before to check it worked without specifying imagePullSecrets
• Create secret
  kubectl create secret generic $DOCKERCONFIG_SECRET_NAME
  --from-file=.dockerconfigjson=$XDG_RUNTIME_DIR/containers/auth.json
  --type=kubernetes.io/dockerconfigjson
  -n your-namespace

do helm install providing values like in this argo app

    helm:
      parameters:
      values: |
        serviceAccounts:
          imagePullSecrets:
          - name: secret-name

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