Clarify 'window' usage in configuration

[sebhoss]

The example config in https://github.com/kubernetes-sigs/prometheus-adapter/blob/master/deploy/manifests/config-map.yaml specifies window: 5m and uses [4m] in some of its queries, yet the code in https://github.com/kubernetes-sigs/prometheus-adapter/blob/master/pkg/config/config.go#L91 mentions that It should match the value used in your containerQuery and nodeQuery if you use a 'rate' function. The example config does use a rate function, but specifies a different value for window which seems to contradict what is written in the code comment.

I could not find any mention of window in the documentation. So what's the point of that option and what value should be set?

[dgrisonnet]

/assign
/triage accepted
/kind documentation