feat(nixos): add gpu module for nvidia config

nix/modules/machine/gpu.nix

@@ -0,0 +1,41 @@
+{ config, ... }:
+let
+  cfg = config.flake;
+in
+{
+  allowedUnfreePackages = [
+    "nvidia-x11"
+    "nvidia-settings"
+  ];
+  flake.modules.nixos.default =
+    {
+      config,
+      pkgs,
+      hostName,
+      ...
+    }:
+    let
+      gpu = cfg.manifest.hosts.nixos.${hostName}.machine.gpu or "";
+    in
+    if gpu == "nvidia" then
+      {
+        hardware = {
+          graphics.enable = true;
+          graphics.extraPackages = [ pkgs.nvidia-vaapi-driver ];
+          nvidia.open = true;
+          nvidia.package = config.boot.kernelPackages.nvidiaPackages.latest;
+        };
+        services.xserver.videoDrivers = [ "nvidia" ];
+        environment.variables = {
+          LIBVA_DRIVER_NAME = "nvidia";
+          __GLX_VENDOR_LIBRARY_NAME = "nvidia";
+          NVD_BACKEND = "direct";
+        };
+        nix.settings.substituters = [ "https://cuda-maintainers.cachix.org" ];
+        nix.settings.trusted-public-keys = [
+          "cuda-maintainers.cachix.org-1:0dq3bujKpuEPMCX6U4WylrUDZ9JyUG0VpVZa7CNfq5E="
+        ];
+      }
+    else
+      { };
+}