feat(user:shell): add system modules for zsh/bash user shell configuration

system/modules/user/shell/zsh/default.nix

@@ -0,0 +1,22 @@
+{ lib, config, pkgs, ... }:
+
+let
+  inherit (lib) mkIf;
+  userShell = config.systemModules.user.shell;
+in
+
+{
+  config = mkIf (userShell == "zsh") {
+    users.users.ooks.shell = pkgs.zsh;
+    programs.zsh = {
+      enable = true;
+      enableCompletion = true;
+      syntaxHighlighting.enable = true;
+      autosuggestions = {
+        enable = true;
+        async = true;
+      };
+    };
+    environment.pathsToLink = ["/share/zsh"];
+  };
+}