refactor: change how inclusion of config works

modules/programs/firefox.nix

@@ -1,7 +1,7 @@
 # Reference https://discourse.nixos.org/t/declare-firefox-extensions-and-settings/36265
 { lib, config, ... }:
-{
-  programs.firefox = lib.mkIf config.programs.firefox.enable {
+lib.mkIf config.programs.firefox.enable {
+  programs.firefox = {
     preferencesStatus = "locked";
     preferences = {
       "browser.bookmarks.restore_default_bookmarks" = false;

modules/programs/steam.nix

@@ -4,8 +4,8 @@
   config,
   ...
 }:
-{
-  programs.steam = lib.mkIf config.programs.steam.enable {
+lib.mkIf config.programs.steam.enable {
+  programs.steam = {
     gamescopeSession.enable = true;
     extest.enable = true;
     localNetworkGameTransfers.openFirewall = true;

modules/programs/thunderbird.nix

@@ -1,6 +1,6 @@
 { lib, config, ... }:
-{
-  programs.thunderbird = lib.mkIf config.programs.thunderbird.enable {
+lib.mkIf config.programs.thunderbird.enable {
+  programs.thunderbird = {
     preferencesStatus = "locked";
     preferences = {
       "mail.biff.play_sound" = false;