added v3.0 branch blurb to readme
added v3.0 branch blurb to readme

jparth11/marbles,Serarmen/marbles,BlockChainPublicDemos/karachain-app-team2,BlockChainPublicDemos/karachain-app-team2,BlockChainPublicDemos/karachain-app-team2,vmd90/marbles,Serarmen/marbles,swetabachhety/ekyc,vmd90/marbles,furuya-s/marbles,sj1chun/marbles,swetabachhety/ekyc,jparth11/marbles,Serarmen/marbles,vmd90/marbles,swetabachhety/ekyc,sj1chun/marbles,JSakchai/KYC-Agent,JSakchai/KYC-Agent,furuya-s/marbles,jparth11/marbles,sj1chun/marbles,JSakchai/KYC-Agent,furuya-s/marbles