add instruction about Security Command Center enablement

Author: daniel-cit

helpers/foundation-deployer/README.md

@@ -11,6 +11,7 @@ Helper tool to deploy the Terraform example foundation using Cloud Build and Clo
 - [Git](https://git-scm.com/book/en/v2/Getting-Started-Installing-Git) version 2.28.0 or later
 - [Terraform](https://www.terraform.io/downloads.html) version 1.5.7 or later
 - See `0-bootstrap` README for additional IAM [requirements](../../0-bootstrap/README.md#prerequisites) on the user deploying the Foundation.
+- To enable Security Command Center, choose a Security Command Center tier and create and grant permissions for the Security Command Center service account as described in [Setting up Security Command Center](https://cloud.google.com/security-command-center/docs/quickstart-security-command-center).
 
 Your environment need to use the same [Terraform](https://www.terraform.io/downloads.html) version used on the build pipeline.
 Otherwise, you might experience Terraform state snapshot lock errors.