Restrict generic-lens to include Product.Constraints for examples
The examples didn't build for me because generic-lens does not have Data.Generics.Product.Constraints so I pinned the generic-lens version.
https://hackage.haskell.org/package/generic-lens-1.2.0.1/docs/Data-Generics-Product-Constraints.html https://hackage.haskell.org/package/generic-lens-2.0.0.0