misc: update helm chart configs and readme (#1751)

* fix wiki helm

* update readme

* include service account as a stub

* use lightweight healthz for readiness and health endpoint

* remove if block for setting DB_TYPE, only postgres is supported in this chart for now

dev/helm/templates/serviceaccount.yaml

@@ -0,0 +1,12 @@
+{{- if .Values.serviceAccount.create -}}
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: {{ include "wiki.serviceAccountName" . }}
+  labels:
+    {{- include "wiki.labels" . | nindent 4 }}
+  {{- with .Values.serviceAccount.annotations }}
+  annotations:
+    {{- toYaml . | nindent 4 }}
+  {{- end }}
+{{- end -}}