make `Set t` a type different from `Dict t ()`
make `Set t` a type different from `Dict t ()`

Dandandan/core,eeue56/core,rgrempel/core,colinmccabe/core,isaacsanders/core,bradurani/core,simonh1000/core,suryagaddipati/core,alexiamcdonald/elm-core,laszlopandy/core,vilterp/core,martinos/core,vilterp/core,suryagaddipati/core,bradurani/core,ThomasWeiser/core,simonh1000/core,ThomasWeiser/core,laszlopandy/core,isaacsanders/core,Pisys/core,rick68/core,colinmccabe/core,rgrempel/core,rick68/core,eeue56/core,martinos/core,Dandandan/core,alexiamcdonald/elm-core,Pisys/core