nero: add Avalonia custom package

hosts/nero/configuration.nix

@@ -93,6 +93,10 @@ in
   };
 
   environment = {
+    sessionVariables = {
+      AVALONIA_SCREEN_SCALE_FACTORS = "DP-2=1.3;HDMI-A-1=1.25;DP-1=1.25";
+    };
+
     systemPackages = with pkgs; [
       qimgv
       zathura
@@ -106,6 +110,7 @@ in
       (callPackage ../../packages/xivlauncher/package.nix { })
       (callPackage ../../packages/aseprite/package.nix { })
       (callPackage ../../packages/aseprite-thumbnailer-kde/package.nix { inherit unstable; })
+      (callPackage ../../packages/undertale-mod-tool/package.nix { })
     ];
   };
 }