Add rateLimited error type.
Add rateLimited error type.

wteiken/letsencrypt,piru/letsencrypt,g1franc/lets-encrypt-preview,goofwear/letsencrypt,sjerdo/letsencrypt,xgin/letsencrypt,Sveder/letsencrypt,twstrike/le_for_patching,lbeltrame/letsencrypt,ghyde/letsencrypt,goofwear/letsencrypt,mitnk/letsencrypt,martindale/letsencrypt,dietsche/letsencrypt,hsduk/lets-encrypt-preview,brentdax/letsencrypt,jsha/letsencrypt,BillKeenan/lets-encrypt-preview,brentdax/letsencrypt,thanatos/lets-encrypt-preview,dietsche/letsencrypt,mrb/letsencrypt,mitnk/letsencrypt,bsmr-misc-forks/letsencrypt,VladimirTyrin/letsencrypt,BillKeenan/lets-encrypt-preview,g1franc/lets-encrypt-preview,xgin/letsencrypt,stweil/letsencrypt,hsduk/lets-encrypt-preview,twstrike/le_for_patching,martindale/letsencrypt,letsencrypt/letsencrypt,sjerdo/letsencrypt,jtl999/certbot,jtl999/certbot,jsha/letsencrypt,DavidGarciaCat/letsencrypt,DavidGarciaCat/letsencrypt,letsencrypt/letsencrypt,stweil/letsencrypt,lbeltrame/letsencrypt,VladimirTyrin/letsencrypt,mrb/letsencrypt,lmcro/letsencrypt,ghyde/letsencrypt,Sveder/letsencrypt,lmcro/letsencrypt,TheBoegl/letsencrypt,kuba/letsencrypt,kuba/letsencrypt,bsmr-misc-forks/letsencrypt,thanatos/lets-encrypt-preview,piru/letsencrypt,TheBoegl/letsencrypt,wteiken/letsencrypt