docs: Mention clap arguments

Author: sbernauer

template/deploy/helm/[[operator]]/templates/deployment.yaml.j2

@@ -43,6 +43,11 @@ spec:
             - mountPath: /etc/stackable/{{ include "operator.appname" . }}/config-spec
               name: config-spec
           env:
+            # The following env vars are passed as clap (think CLI) arguments to the operator.
+            # They are picked up by clap using the structs defied in
+            # https://github.com/stackabletech/operator-rs/blob/main/crates/stackable-operator/src/cli.rs
+            # (currently "ProductOperatorRun").
+            # You can read there about the expected values and purposes.
             - name: OPERATOR_IMAGE
               # Tilt can use annotations as image paths, but not env variables
               valueFrom: