chore: move module/constants.nix to lib/default.nix

modules/system-dependent.nix

@@ -0,0 +1,31 @@
+{ config, lib, pkgs, ... }:
+with lib;
+{
+  options.niveum = {
+    wirelessInterface = mkOption { type = types.str; };
+
+    batteryName = mkOption { type = types.str; };
+
+    promptColours = let
+      colours16 = types.enum [
+        "black"
+        "red"
+        "green"
+        "yellow"
+        "blue"
+        "magenta"
+        "cyan"
+        "white"
+      ];
+    in {
+      success = mkOption {
+        type = colours16;
+        default = "green";
+      };
+      failure = mkOption {
+        type = colours16;
+        default = "red";
+      };
+    };
+  };
+}