Add Documentation for Landing Zone on Guardrails Coverage/Implementation

**Is your feature request related to a problem? Please describe.**
As a client who is onboarding onto Google Cloud I would like to know how the Landing Zone is achieving Guardrails Policy.

**Describe the solution you'd like**
Add Documentation around how the Guardrails are being met and what resources are being provisioned.

**Describe alternatives you've considered**
n/a

**Additional context**
n/a