fix: add option to not install package for sway / swaylock

avoid problems with nix on Debian

modules/home-manager/desktop/sway/includes/swaylock.nix

@@ -1,4 +1,4 @@
-{ config, lib, ... }: 
+{ config, lib, pkgs, ... }: 
 with lib;
 let
   cfg = config.modules.desktop.sway;
@@ -7,6 +7,10 @@ in
   config = mkIf config.modules.desktop.sway.enable {
     programs.swaylock = {
       enable = true;
+      package =
+        if cfg.installPackage
+        then pkgs.swaylock
+        else pkgs.emptyDirectory;
       settings = {
         image = "${cfg.wallpapers.lockscreen}";
         scaling = "center";