Docs: add GKE whitepaper to GCP VM instructions

Add note of Google provided Production-ready GitLab on GKE whitepaper
to the GCP vm installations page

doc/install/google_cloud_platform/index.md

@@ -8,6 +8,13 @@ description: 'Learn how to install a GitLab instance on Google Cloud Platform.'
 
 Getting started with GitLab on a [Google Cloud Platform (GCP)][gcp] instance is quick and easy.
 
+NOTE: **Note:** Google provides a whitepaper for [deploying production-ready GitLab on
+Google Kubernetes Engine][whitepaper], including all steps and external
+resource configuration. These are alternative to using a GCP VM, and use
+the [Cloud native GitLab Helm chart](https://docs.gitlab.com/charts)
+
+[whitepaper]: https://cloud.google.com/solutions/deploying-production-ready-gitlab-on-gke
+
 ## Prerequisites
 
 There are only two prerequisites in order to install GitLab on GCP: