Refactor: Rename hardware.* by category

Fix #5

modules/system/boot/default.nix

@@ -0,0 +1,7 @@
+{ ... }:
+
+{
+  imports = [
+    ./plymouth.nix
+  ];
+}

modules/system/boot/plymouth.nix

@@ -0,0 +1,16 @@
+{ config, lib, ... }:
+
+with lib;
+let
+  cfg = config.modules.system.boot.plymouth;
+in
+{
+  options.modules.system.boot.plymouth = {
+    enable = mkEnableOption ''
+      Enable plymouth with my custom configurations
+    '';
+  };
+  config = mkIf cfg.enable {
+    boot.plymouth.enable = true;
+  };
+}