home: extract 'comma' into its own module

home/comma.nix

@@ -0,0 +1,15 @@
+{ config, lib, pkgs, ... }:
+let
+  cfg = config.my.home.comma;
+in
+{
+  options.my.home.comma = with lib; {
+    enable = my.mkDisableOption "comma configuration";
+  };
+
+  config = lib.mkIf cfg.enable {
+    home.packages = with pkgs; [
+      ambroisie.comma
+    ];
+  };
+}