Add build-configs from its derivation

It currently uses a local version of `build-configs`. I need to look
into how to get it to with Nix and a private GitHub repository.

lib/shared/home-manager-packages.nix

@@ -3,6 +3,8 @@ let
   php = pkgs.php82;
   phpPackages = pkgs.php82Packages;
 in with pkgs; [
+  inputs.build-configs.packages.${pkgs.system}.default
+
   awscli2
   bitwarden-cli
   bottom