nix: add module for desktop applications

nix/modules/applications.nix

@@ -0,0 +1,23 @@
+{ config, lib, pkgs }:
+
+{
+  environment.systemPackages = with pkgs; [
+    gimp
+    audacity
+    obsidian
+    cinny-desktop
+  ];
+
+  programs.firefox.enable = true;
+
+  programs.kdeconnect.enable = true;
+  systemd.user.services.kdeconnectd = {
+    enable = true;
+    after = [ "default.target" ];
+    description = "kdeconnectd";
+    serviceConfig = {
+        Type = "simple";
+        ExecStart = "${pkgs.kdeconnectd}/bin/kdeconnectd";
+    };
+  };
+}