Add ghc-imported-from to build-constraints.yaml
Add ghc-imported-from to build-constraints.yaml

I've updated my package ghc-imported-from to build with Stack and now I'd like for users to be able to install it from stack.

https://hackage.haskell.org/package/ghc-imported-from
GregorySchwartz/stackage,codedmart/stackage,ethercrow/stackage,agrafix/stackage,alanz/stackage,simonmichael/stackage,fpco/stackage,mrkkrp/stackage,athanclark/stackage,asr/stackage,ygale/stackage,michalkonecny/stackage,judah/stackage,soenkehahn/stackage,jaspervdj/stackage,jonschoning/stackage,DanielG/stackage,christiaanb/stackage,phadej/stackage,garetxe/stackage,mgajda/stackage,mstksg/stackage,wereHamster/stackage,Daniel-Diaz/stackage,massysett/stackage,nomeata/stackage,creichert/stackage,clinty/stackage,Shimuuar/stackage,l29ah/stackage,k0ral/stackage,bartavelle/stackage,marcinmrotek/stackage,peti/stackage,brendanhay/stackage,stackbuilders/stackage,lwm/stackage,spencerjanssen/stackage,int-index/stackage,fimad/stackage,iand675/stackage,phaazon/stackage,Gabriel439/stackage