Adding the RDDL description of vital sign
Adding the RDDL description of vital sign

Xodarap/health-data-standards,okeefm/health-data-standards,PheMA/health-data-standards,okeefm/health-data-standards,thecristen/health-data-standards,projectcypress/health-data-standards,PheMA/health-data-standards,Xodarap/health-data-standards,thecristen/health-data-standards,projectcypress/health-data-standards