Add wallpaper to display manager

hosts/desktop.nix

@@ -1,5 +1,8 @@
 { config, pkgs, ... }:
 
+let
+  colors = import ../colors;
+in
 {
   services = {
    xserver = {
@@ -19,6 +22,7 @@
               package = pkgs.nordic;
             };
           };
+          background = ../wallpapers/${colors.wallpaper};
         };
         defaultSession = "none+i3";
       };