⏪️(helm) bring back helm chart

This is a revert of 1da5a removing actual deployments and keeping
only the dev environment in Tilt.

The clean-up was a bit heavy handed. We should keep the Helm
chart to the development repository and move away only the
deployment configuration.

src/helm/extra/templates/postgresql.yaml

@@ -0,0 +1,7 @@
+apiVersion: core.libre.sh/v1alpha1
+kind: Postgres
+metadata:
+  name: postgresql
+  namespace: {{ .Release.Namespace | quote }}
+spec:
+  database: impress