Add imagePullSecret to the `default` helm create template

This relates to [#3529](https://github.com/helm/helm/issues/3529).
It adds image.pullSecret to the default generate blank chart
when the user does `helm create`.

Signed-off-by: Don Bowman <don@agilicus.com>

pkg/chartutil/create.go

@@ -62,6 +62,7 @@ image:
   repository: nginx
   tag: stable
   pullPolicy: IfNotPresent
+  # pullSecret: my_secret
 
 nameOverride: ""
 fullnameOverride: ""
@@ -189,6 +190,10 @@ spec:
         app.kubernetes.io/name: {{ include "<CHARTNAME>.name" . }}
         app.kubernetes.io/instance: {{ .Release.Name }}
     spec:
+      {{- if .Values.image.pullSecret -}}
+      imagePullSecrets:
+        - name: {{ .Values.image.pullSecret }}
+      {{- end }}
       containers:
         - name: {{ .Chart.Name }}
           image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"