Add guidance for new nats configuration values.

Signed-off-by: Han Verstraete (OpenFaaS Ltd) <[email protected]>

Author: welteki

chart/openfaas/values.yaml

@@ -238,12 +238,16 @@ alertmanager:
       memory: "50Mi"
 
 stan:
+  # Image used for nats deployment when using async with NATS-Streaming.
   image: nats-streaming:0.22.0
 
 # NATS is required for async
 nats:
   channel: "faas-request"
   queueMode: ""
+  # Stream replication is set to 1 by default. This is only recommended for development.
+  # For production a value of at least 3 is recommended for NATS JetStream to be resilient.
+  # See https://github.com/openfaas/openfaas-pro/blob/master/jetstream.md
   streamReplication: 1
   external:
     clusterName: ""