Add integration test

[Schultzer]

This PR adds an integration workflow for all the repositories.

This will use the current branch, SEE elixir-cldr/cldr_territories#43, for more context.

For a repository that requires ex_cldr, the mix files should change the following. This is similar to how Ecto approaches this: https://github.com/elixir-ecto/ecto_sql/blob/master/mix.exs#L53-L81

   defp deps do
     [
        {:ex_cldr, cldr_dep()},
        ...
     ]
   end


  defp cldr_dep() do
    if path = System.get_env("CLDR_PATH") do
      [path: path]
    else
      "~> 2.38"
    end
  end