add nonempty-containers to stackage
add nonempty-containers to stackage

clinty/stackage,soenkehahn/stackage,jonschoning/stackage,ethercrow/stackage,athanclark/stackage,fimad/stackage,wereHamster/stackage,Daniel-Diaz/stackage,michalkonecny/stackage,peti/stackage,asr/stackage,simonmichael/stackage,massysett/stackage,stackbuilders/stackage,mrkkrp/stackage,int-index/stackage,spencerjanssen/stackage,mstksg/stackage,iand675/stackage,fpco/stackage