add more description

Author: medyagh

.github/workflows/update-kubernetes-versions-list.yml

@@ -42,3 +42,5 @@ jobs:
           title: 'Update Kubernetes versions list'
           body: |
             This PR was auto-generated by `make update-kubernetes-versions-list` using [update-kubernetes-versions-list.yml](https://github.com/kubernetes/minikube/tree/master/.github/workflows/update-kubernetes-versions-list.yml) CI Workflow.
+            The purpose of this ValidKubernetesVersions in the code is, to check a kuberentes version is valid without checking Github on first try
+            and if the version is not valid, it will check Github for the latest valid versions.