[shell] Moves shell utilities to shell.nix. Adds direnv to development.nix

home-manager/features/development/development.nix

@@ -1,4 +1,4 @@
-{ ... }:
+{ pkgs, ... }:
 {
   imports = [
     # Dev apps
@@ -12,4 +12,8 @@
     ./nix.nix
     ./lua.nix
   ];
+
+  home.packages = with pkgs; [
+    direnv
+  ];
 }