Configure replicas, as discussed in #42

[jeanpommier]

Allows to turn off some apps, for instance for maintenance operations

see #42

[edevosc2c]

I think instead of | default 1, just uncomment replicas: 1 in the values.yaml, then 1 will always be used "by default".

Could you name the helm value replicaCount instead of replicas? It's a standard in the "Kubernetes world": https://www.automox.com/blog/kubernetes-helm-101 and https://helm.sh/docs/chart_template_guide/getting_started/

Thank you

[jeanpommier]

Fine by me. Done. Thanks for the review