feat: sway configuration

- Change the mod key to Alt.
- Change the keyboard input language to UK.
- Replace dmenu with wofi.
- Disable the laptop screen when used in clam mode (lid closed with an
  external monitor).
- Override the GTK theme to ensure that a dark theme is used in all apps
  (e.g. Firefox).

See:

- https://github.com/swaywm/sway/wiki#clamshell-mode
- https://wiki.archlinux.org/title/Sway#Keymap

system/nixos/nixedo/configuration.nix

@@ -4,7 +4,22 @@
 
 { config, pkgs, ... }:
 
-let nixpkgs = import ../../shared/nixpkgs.nix { };
+let
+  nixpkgs = import ../../shared/nixpkgs.nix { };
+
+  configure-gtk = pkgs.writeTextFile {
+      name = "configure-gtk";
+      destination = "/bin/configure-gtk";
+      executable = true;
+      text = let
+        schema = pkgs.gsettings-desktop-schemas;
+        datadir = "${schema}/share/gsettings-schemas/${schema.name}";
+      in ''
+        export XDG_DATA_DIRS=${datadir}:$XDG_DATA_DIRS
+        gnome_schema=org.gnome.desktop.interface
+        gsettings set $gnome_schema gtk-theme 'Breeze Dark'
+        '';
+  };
 in {
   nixpkgs = nixpkgs;
 
@@ -103,14 +118,22 @@ in {
   # $ nix search wget
   environment.systemPackages = with pkgs;
     [
+      configure-gtk
       swayidle
       swaylock
     ];
 
-    programs.sway = {
-      enable = true;
-      wrapperFeatures.gtk = true;
-    };
+  xdg.portal = {
+    enable = true;
+    wlr.enable = true;
+    # gtk portal needed to make gtk apps happy
+    extraPortals = [ pkgs.xdg-desktop-portal-gtk ];
+  };
+
+  programs.sway = {
+    enable = true;
+    wrapperFeatures.gtk = true;
+  };
 
   # Some programs need SUID wrappers, can be configured further or are
   # started in user sessions.