GONRG-3661 update GCP readme
Add readme for GCP environment
Starting on April 8th, The Open Group will require Two Factor Authentication for all GitLab users. For instructions on setting up 2FA, see the Knowledge Article or GitLab Documentation. Note in particular that any HTTPS clones will require the use of a Personal Access Token (rather than a user’s password) once 2FA is enabled.
Add readme for GCP environment