Add upper bounds for hjsonschema.
Add upper bounds for hjsonschema.

Please see https://github.com/seagreen/hjsonschema/issues/48.

stackbuilders/stackage,Shimuuar/stackage,peti/stackage,clinty/stackage,lwm/stackage,GregorySchwartz/stackage,judah/stackage,mrkkrp/stackage,massysett/stackage,fimad/stackage,spencerjanssen/stackage,k0ral/stackage,ygale/stackage,Daniel-Diaz/stackage,simonmichael/stackage,int-index/stackage,garetxe/stackage,mgajda/stackage,creichert/stackage,alanz/stackage,phaazon/stackage,asr/stackage,soenkehahn/stackage,ethercrow/stackage,fpco/stackage,michalkonecny/stackage,jonschoning/stackage,wereHamster/stackage,iand675/stackage,mstksg/stackage,athanclark/stackage