Add alejandra nix formatter and integrate into NixOS flake

modules/packages/essentials.nix

@@ -1,4 +1,4 @@
-{config, pkgs, libs, inputs, nix-flatpak, ...}:
+{config, pkgs, libs, inputs, system, alejandra, ...}:
 {
   environment.systemPackages = with pkgs; [
     #Essentials (CLI Only)
@@ -45,5 +45,6 @@
     kdePackages.ksshaskpass
     ntfs3g
     appimage-run
+    alejandra.defaultPackage.${system}
   ];
 }