Login Xkb setup

      displayManager = {
          lightdm.enable = true;
          sessionCommands = ''
              # NOTE: Depends on repository xkb.
              /home/kristoffer/xkb/scripts/keyboard-setup \
                  "twin-dexter(no-p5),twin-dexter(no-4)"
              export GTK_IM_MODULE=xim
          '';
      };