flakes: Migrate the config and miku to flakes

modules/programs/xournalpp/default.nix

@@ -1,10 +1,19 @@
-{ config, pkgs, ... }:
+{ config, lib, pkgs, ... }:
 
-{
-  environment.systemPackages = with pkgs; [ xournalpp-git ];
+let
+  cfg = config.ptw.programs.xournalpp;
+in {
+  options.ptw.programs.xournalpp = {
+    enable = lib.mkEnableOption "Install xournalpp";
+    configure = lib.mkEnableOption "Configure xournalpp using HomeManager";
+  };
 
- #home-manager.users."${config.system.singleUser}".home.file = {
- #  ".xournalpp/settings.xml".source = ./settings.xml;
- #  ".xournalpp/toolbar.ini".source = ./toolbar.ini;
- #};
+  config = lib.mkIf cfg.enable {
+    environment.systemPackages = with pkgs; [ xournalpp-git ];
+
+    home-manager.users."${config.ptw.system.singleUser}".home.file = lib.mkIf cfg.configure {
+      ".xournalpp/settings.xml".source = ./settings.xml;
+      ".xournalpp/toolbar.ini".source = ./toolbar.ini;
+    };
+  };
 }