Update index.html.md by adding in the Google Docs link to Reference Customers
Added Google Docs link to Reference Customers in Onboarding handbook so new employees can request access to it directly without searching for it.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Added Google Docs link to Reference Customers in Onboarding handbook so new employees can request access to it directly without searching for it.