feat: add zsh as default shell

systems/modules/common.nix

@@ -1,4 +1,10 @@
 {pkgs, ...}: {
+  imports = [
+    ./networking.nix
+    ./shell.nix
+    ./stylix.nix
+  ];
+
   users.users.rafiq = {
     isNormalUser = true;
     description = "rafiq";

systems/modules/programs/zsh.nix

@@ -0,0 +1,7 @@
+{pkgs, ...}: {
+  programs.zsh = {
+    enable = true;
+  };
+  users.defaultUserShell = pkgs.zsh;
+  environment.pathsToLink = ["/share/zsh"]; # enables completion
+}

systems/modules/shell.nix

@@ -0,0 +1,5 @@
+{
+  imports = [
+    ./programs/zsh.nix
+  ];
+}