fix: add shellcheck

Also move user specific packages to the user section.

configuration.nix

@@ -72,21 +72,13 @@
   environment = {
     systemPackages = with pkgs; [
       curl
-      deno
-      distrobox
-      firefox
       gcc
       git
       gnumake
       htop
       jq
       lesspipe
-      luajitPackages.luarocks
-      mage
-      pwgen
-      tmux
       vim
-      xdg-user-dirs
     ];
 
     variables = rec {
@@ -175,8 +167,17 @@
     description  = "Dan Anglin";
     extraGroups  = [ "networkmanager" "wheel" "docker"];
     packages = with pkgs; [
+      deno
+      distrobox
+      firefox
       lf
+      luajitPackages.luarocks
+      mage
+      pwgen
+      shellcheck
+      tmux
       unstable.neovim
+      xdg-user-dirs
     ];
   };