Run CompatHelper on sub-packages as well

[visr]

This makes sure we run CompatHelper on all sub-packages, such that for instance Makie breaking releases (#113) are not forgotten.

          import CompatHelper
          CompatHelper.main(; subdirs=[
              ".",
              "GeoInterfaceMakie",
              "GeoInterfaceRecipes",
          ])

The diff is a bit larger since I update to the latest suggested workflow from https://github.com/JuliaRegistries/CompatHelper.jl.

Actually I don't think the old CompatHelper ever worked since I don't see it installing Julia or using Actions.