modules/locale: add locale module

modules/modules/locale.nix

@@ -0,0 +1,22 @@
+{ config, options, lib, ... }:
+with lib;
+with lib.hlissner;
+let
+  cfg = config.modules.locale;
+in
+{
+  options.modules.locale = {
+    keymap = mkOpt "us";
+    locale = mkOpt "en_us.UTF-8";
+    timezone = mkOpt "America/New_York";
+  };
+
+  config = {
+    console.keyMap = mkDefault cfg.keymap;
+    services.xserver.layout = mkDefault cfg.keymap;
+
+    i18n.defaultLocale = cfg.locale;
+
+    time.timeZone = cfg.timezone;
+  };
+}