[Packages + Desktop] Add many packages good for default desktop use

desktop.nix

@@ -188,8 +188,11 @@ in {
       yakuake
       pinentry-qt
       plasma-pa
-      ark
+      ark.override {
+        unfreeEnableUnrar = true;
+      }
       p7zip
+      vlc
     ];
 
     networking.networkmanager = {

packages.nix

@@ -70,6 +70,10 @@ in
       rsyncOptimized
       htop
       cachix
+      psmisc # killall, etc.
+      par2cmdline # .par2 archive verification
+      schedtool
+      python3
     ];
 
     programs.ssh.package = pkgs.opensshOptimized;