doc: add branch.io use case into production users
doc: add branch.io use case into production users

coreos/etcd,etcd-io/etcd,sinsharat/etcd,vimalk78/etcd,bluebreezecf/etcd,handsomesun/etcd,a-robinson/etcd,yudai/etcd,fanminshi/etcd,ajityagaty/etcd,akauppi/etcd,glevand/coreos--etcd,sebrandon1/etcd,mqliang/etcd,heyitsanthony/etcd,handsomesun/etcd,ajityagaty/etcd,xiang90/etcd,li-ang/etcd,mickep76/etcd,yudai/etcd,mqliang/etcd,xiang90/etcd,YuleiXiao/etcd,mkumatag/etcd,rnaveiras/etcd,mickep76/etcd,YuleiXiao/etcd,lumjjb/etcd,tguangch/etcd,plasticbox/etcd,jlamillan/etcd,heyitsanthony/etcd,cockroachdb/etcd,etcd-io/etcd,cockroachdb/etcd,whuwxl/etcd,mkumatag/etcd,akauppi/etcd,a-robinson/etcd,bluebreezecf/etcd,visheshnp/etcd,mkumatag/etcd,coreos/etcd,gyuho/etcd,etcd-io/etcd,visheshnp/etcd,armstrongli/etcd,dannysauer/etcd,bdarnell/etcd,whuwxl/etcd,lumjjb/etcd,tguangch/etcd,plasticbox/etcd,rnaveiras/etcd,joshix/etcd,glevand/coreos--etcd,lorneli/etcd,rnaveiras/etcd,jlamillan/etcd,sebrandon1/etcd,armstrongli/etcd,gyuho/etcd,fanminshi/etcd,lorneli/etcd,ajityagaty/etcd,sinsharat/etcd,dannysauer/etcd,bdarnell/etcd,mqliang/etcd,vimalk78/etcd,joshix/etcd,li-ang/etcd