Add a CI check for building with Cabal
Add a CI check for building with Cabal

The idea is that this ensures
1. that it's easy for contributers to hack on PostgREST without
   getting nix set up
2. we see things break more easily outside the very controlled nix
   environment (e.g. it would be easy to add a GHC 9.4.2 build here)

steve-chavez/postgrest,begriffs/postgrest,steve-chavez/postgrest