feat(home-manager): set GTK theme and git signing format

nixos/home-manager.nix

@@ -1,4 +1,4 @@
-{ pkgs, lib, nixos, ... }:
+{ config, pkgs, lib, nixos, ... }:
 {
   # Automatic garbage collection of old home-manager generations
   nix.gc = {
@@ -102,6 +102,13 @@
       name = "Numix-Circle";
     };
 
+    theme = {
+      package = pkgs.arc-theme;
+      name = "Arc";
+    };
+
+    gtk4.theme = config.gtk.theme;
+
     font = {
       package = pkgs.noto-fonts-color-emoji;
       name = "Noto Sans";

nixos/imalison.nix

@@ -6,6 +6,7 @@
     ];
 
     programs.git.enable = true;
+    programs.git.signing.format = "openpgp";
     programs.gh = {
       enable = true;
       settings.git_protocol = "ssh";