Add description on when to upgrade supported Kubernetes version (#3049)

CONTRIBUTING.md

@@ -87,7 +87,10 @@ See the [Container Builder documentation](https://cloud.google.com/container-bui
 how to edit and expand the build process.
 
 ## Kubernetes Versions Update
-Each version of Agones supports specific versions of Kubernetes by following the [version update policy](https://agones.dev/site/docs/installation/#agones-and-kubernetes-supported-versions). Please follow the steps below to update the Kubernetes versions supported.
+### When to update supported Kubernetes Versions
+As documented in the [version update policy](https://agones.dev/site/docs/installation/#agones-and-kubernetes-supported-versions), each version of Agones supports 3 releases of Kubernetes. The newest supported version is the latest available version in the GKE Rapid channel and at least one of the 3 supported version is supported by each of the major cloud providers (EKS and AKS). This means whenever a new minor version is available in the [GKE Rapid channel](https://cloud.google.com/kubernetes-engine/docs/release-notes-rapid), we should check whether we can roll forward the supported versions.
+### How to update supported Kubernetes Versions
+Please follow the steps below to update the Kubernetes versions supported.
 
 1. Create a Issue from the [kubernetes update issue template](../../.github/ISSUE_TEMPLATE/kubernetes_update.md) with the newly supported versions.
 2. Complete all items in the issue checklist.

site/content/en/docs/Installation/_index.md

@@ -39,7 +39,7 @@ For all the platforms in Alpha, we would appreciate testing and bug reports on a
 
 ## Agones and Kubernetes Supported Versions
 
-Agones will support 3 releases of Kubernetes, targeting the newest version as being the [default version in the GKE Rapid channel](https://cloud.google.com/kubernetes-engine/docs/release-notes#current_versions). However, we will ensure that at least one of the 3 versions chosen for each Agones release is supported by each of the major cloud providers (EKS and AKS). The vendored version of client-go will be aligned with the middle of the three supported Kubernetes versions. When a new version of Agones supports new versions of Kubernetes, it is explicitly called out in the [release notes](https://agones.dev/site/blog/releases/).
+Agones will support 3 releases of Kubernetes, targeting the newest version as being the [latest available version in the GKE Rapid channel](https://cloud.google.com/kubernetes-engine/docs/release-notes#current_versions). However, we will ensure that at least one of the 3 versions chosen for each Agones release is supported by each of the major cloud providers (EKS and AKS). The vendored version of client-go will be aligned with the middle of the three supported Kubernetes versions. When a new version of Agones supports new versions of Kubernetes, it is explicitly called out in the [release notes](https://agones.dev/site/blog/releases/).
 
 The following table lists recent Agones versions and their corresponding required Kubernetes versions: