docs: explain skew policy between the kubectl plugin and the controller (#4300)

* docs: explain version skew policy

Signed-off-by: Kostis Kapelonis <[email protected]>

* docs: explain version skew policy - added links

Signed-off-by: Kostis Kapelonis <[email protected]>

---------

Signed-off-by: Kostis Kapelonis <[email protected]>

Author: kostis-codefresh

docs/FAQ.md

@@ -47,6 +47,10 @@ Yes. A k8s cluster can run multiple replicas of Argo-rollouts controllers to ach
 
 No you cannot do that (even though Argo CD can work that way). This is by design because the Rollout is a custom resource unknown to vanilla Kubernetes. You need the Rollout CRD as well as the controller in the deployment cluster (every cluster that will use workloads with Rollouts).
 
+### What is the version skew policy between the controller and the kubectl plugin?
+
+The Argo Rollout CLI/Kubectl plugin just patches the Rollout object or reads fields from it. [There is no separate "Argo Rollouts API"](../best-practices#there-is-no-argo-rollouts-api). Old versions of the plugin might not understand new fields that are added in the [Rollout specification](../features/specification/). We have never made a breaking change intentionally (removed something from the Rollout Spec). So old clients should work even with newer Rollout versions (excluding new features).
+
 ## Rollouts
 
 ### Which deployment strategies does Argo Rollouts support?