changes before turning into a flake

non-nix/download_hs/default.nix

@@ -0,0 +1,12 @@
+let pkgs = import <nixpkgs> { };
+in pkgs.haskellPackages.developPackage {
+  root = ./.;
+  modifier = drv:
+    pkgs.haskell.lib.addBuildTools drv (with pkgs.haskellPackages; [
+      cabal-install
+      ghcid
+      haskell-language-server
+      fourmolu
+      regex
+    ]);
+}