zsh: init zsh module

hosts/shared/zsh.nix

@@ -0,0 +1,31 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+let
+  cfg = config.alqueva.shells.zsh;
+
+  inherit (lib.modules) mkIf;
+  inherit (lib.options) mkEnableOption mkPackageOption;
+in
+{
+  options.alqueva.shells.zsh = {
+    enable = mkEnableOption "zsh";
+    package = mkPackageOption pkgs "zsh" { };
+  };
+  config = mkIf cfg.enable {
+    environment = {
+      systemPackages = [ cfg.package ];
+      shells = [ cfg.package ];
+    };
+
+    programs.zsh = {
+      enable = true;
+      enableCompletion = true;
+      syntaxHighlighting.enable = true;
+      autosuggestions.enable = true;
+    };
+  };
+}