[AnVIL DX] Add RAS banner

[MillenniumFalconMechanic]

Overview

Add the following banner (see Slack):

As part of new federal government security policies, Terra is required to integrate with the NIH Researcher Authentication Service (RAS) for identity proofing and enhanced security.  In order to link your NIH authorization to Terra, users of eRA Commons must transition to the use of Login.gov or ID.me credentials to access AnVIL controlled-access data in Terra. See here for more details and instructions.