doc: add proxy promotion doc
doc: add proxy promotion doc

ajityagaty/etcd,endocode/etcd,lumjjb/etcd,achanda/etcd,cockroachdb/etcd,a-robinson/etcd,raoofm/etcd,armstrongli/etcd,tguangch/etcd,lorneli/etcd,msanterre/etcd,qqsun8819/etcd,wowsoso/etcd,jeremyeder/etcd,visheshnp/etcd,bluebreezecf/etcd,heyitsanthony/etcd,hongchaodeng/etcd,insequent/etcd,chipironcin/etcd,improbable-io/etcd,sofuture/etcd,siddontang/etcd,swingbach/etcd,ravigadde/etcd,achanda/etcd,wantonsolutions/dinv-etcd,westhood/etcd,bluebreezecf/etcd,glycerine/etcd,beni55/etcd,fanminshi/etcd,etcd-io/etcd,vimalk78/etcd,luxas/etcd,rchicoli/etcd,wantonsolutions/dinv-etcd,fanminshi/etcd,combk8s/etcd,gyuho/etcd,etcd-io/etcd,yichengq/etcd,mqliang/etcd,sayden/etcd,Eagle-X/etcd,ajityagaty/etcd,oscarrr110/etcd,wantonsolutions/dinv-etcd,combk8s/etcd,handsomesun/etcd,gyuho/etcd,CrazyJvm/etcd,cockroachdb/etcd,HideoYamauchi/etcd,CrazyJvm/etcd,hroyrh/etcd,lorneli/etcd,coreos/etcd,ajityagaty/etcd,rnaveiras/etcd,sayden/etcd,ktateish/etcd,chipironcin/etcd,linuxcer/etcd,xychu/etcd,joshix/etcd,bdarnell/etcd,whuwxl/etcd,sinsharat/etcd,joshix/etcd,Timer/etcd,OyTao/etcd_learning,yudai/etcd,akauppi/etcd,yudai/etcd,dannysauer/etcd,cchamplin/etcd,raoofm/etcd,handsomesun/etcd,tamird/etcd,mike-lerch/etcd,mkumatag/etcd,beni55/etcd,asim/etcd,mkumatag/etcd,YuleiXiao/etcd,coreos/etcd,siddontang/etcd,rnaveiras/etcd,pauldallen/etcd,mickep76/etcd,xiang90/etcd,oscarrr110/etcd,jlamillan/etcd,asim/etcd,shawnps/etcd,glevand/coreos--etcd,sebrandon1/etcd,shawnps/etcd,kkaneda/etcd,etcd-io/etcd,tamird/etcd,StorReduce/etcd,glycerine/etcd,whuwxl/etcd,purpleidea/etcd,Eagle-X/etcd,akauppi/etcd,qqsun8819/etcd,vimalk78/etcd,endocode/etcd,StorReduce/etcd,nekto0n/etcd,mkumatag/etcd,a-robinson/etcd,jonboulle/etcd,ravigadde/etcd,fasaxc/etcd,HideoYamauchi/etcd,heyitsanthony/etcd,xychu/etcd,armstrongli/etcd,linuxcer/etcd,lumjjb/etcd,msanterre/etcd,dnaeon/etcd,luxas/etcd,jlamillan/etcd,OyTao/etcd_learning,mike-lerch/etcd,tguangch/etcd,yichengq/etcd,jeremyeder/etcd,hongchaodeng/etcd,sofuture/etcd,ktateish/etcd,sinsharat/etcd,fasaxc/etcd,insequent/etcd,pauldallen/etcd,li-ang/etcd,fasaxc/etcd,purpleidea/etcd,rchicoli/etcd,plasticbox/etcd,improbable-io/etcd,hroyrh/etcd,zaphod-concur/etcd,cchamplin/etcd,wowsoso/etcd,jonboulle/etcd,mqliang/etcd,YuleiXiao/etcd,dnaeon/etcd,westhood/etcd,Timer/etcd,visheshnp/etcd,zaphod-concur/etcd,bdarnell/etcd,glevand/coreos--etcd,dannysauer/etcd,swingbach/etcd,plasticbox/etcd,sebrandon1/etcd,xiang90/etcd,nekto0n/etcd,mickep76/etcd,rnaveiras/etcd,li-ang/etcd,mqliang/etcd,kkaneda/etcd