refactor(nixos): move usb config to its own module

modules/nixos/hardware/usb/default.nix

@@ -0,0 +1,46 @@
+{
+  config,
+  pkgs,
+  lib,
+  ...
+}:
+let
+  inherit (lib)
+    mkEnableOption
+    mkIf
+    mkMerge
+    singleton
+    ;
+  cfg = config.hardware.usb;
+in
+{
+  options.hardware.usb = {
+    automount = mkEnableOption "";
+    enableQmk = mkEnableOption "";
+  };
+
+  config = mkMerge [
+    (mkIf cfg.automount {
+      services.udisks2.enable = true;
+      home-manager.sharedModules = singleton {
+        services.udiskie = {
+          enable = true;
+          automount = true;
+          notify = true;
+        };
+      };
+    })
+    (mkIf cfg.enableQmk {
+      hardware.keyboard.qmk.enable = true;
+      services.udev = {
+        packages = with pkgs; [
+          vial
+          via
+          qmk
+          qmk-udev-rules
+          qmk_hid
+        ];
+      };
+    })
+  ];
+}