Add usage instructions to README
Add usage instructions to README

ministryofjustice/defence-request-service-omniauth-dsds,ministryofjustice/ds-auth-omniauth,ministryofjustice/defence-request-service-omniauth-dsds,ministryofjustice/ds-auth-omniauth,ministryofjustice/ds-auth-omniauth,ministryofjustice/defence-request-service-omniauth-dsds