Added initial upgrade docs

docs/eks_version_upgrades.md

@@ -0,0 +1,42 @@
+# EKS Workshop - EKS Version Upgrades
+
+This document outlines the procedure to upgrade EKS versions for this workshop.
+
+## Identify a kubectl version
+
+The easiest way to do this seems to be to use the CHANGELOG file. For example for Kubernetes 1.25 you can find the latest version here:
+
+https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG/CHANGELOG-1.25.md
+
+Alter that URL for the Kubernetes version you are updating to.
+
+## Identify an AMI release
+
+We never want to use the latest AMI due to the worker node upgrade scenario. This command will provide the name of the correct AMI for a specific version:
+
+```
+$ aws ec2 describe-images \
+    --owners amazon \
+    --filters "Name=name,Values=amazon-eks-node-1.25*" --query "Images[1].[Name,Description]" --output text
+amazon-eks-node-1.25-v20230304  EKS Kubernetes Worker AMI with AmazonLinux2 image, (k8s: 1.25.6, containerd: 1.6.6-1.amzn2.0.2)
+```
+
+The name of the release expected by the EKS API for this AMI would be:
+
+```
+1.25.6-20230304
+```
+
+This is a combination of:
+- the `k8s` value (`1.25.6`)
+- the date string without the `v` (`20230304`)
+
+## Update the version numbers
+
+There are various places that reference the Kubernetes versions (Kubernetes, kubectl and AMI), make sure to update them all:
+
+1. Docusaurus variables: `website/docusaurus.config.js`
+1. IDE installer: `lab/scripts/installer.sh`
+1. eksctl: `cluster/eksctl/cluster.yaml`
+1. Terraform: `cluster/terraform/variables.tf`
+1. Common kubectl: `/hack/lib/kubectl-version.sh`