Add README.md for the Importer
Add README.md for the Importer

PiperOrigin-RevId: 303798375

GoogleCloudPlatform/healthcare,GoogleCloudPlatform/healthcare,GoogleCloudPlatform/healthcare,GoogleCloudPlatform/healthcare,GoogleCloudPlatform/healthcare,GoogleCloudPlatform/healthcare,GoogleCloudPlatform/healthcare,GoogleCloudPlatform/healthcare