nixos/e16: add e16 module

nixos/modules/services/x11/window-managers/default.nix

@@ -15,6 +15,7 @@ in
     ./cwm.nix
     ./clfswm.nix
     ./dwm.nix
+    ./e16.nix
     ./evilwm.nix
     ./exwm.nix
     ./fluxbox.nix

nixos/modules/services/x11/window-managers/e16.nix

@@ -0,0 +1,26 @@
+{ config , lib , pkgs , ... }:
+
+with lib;
+
+let
+  cfg = config.services.xserver.windowManager.e16;
+in
+{
+  ###### interface
+  options = {
+    services.xserver.windowManager.e16.enable = mkEnableOption "e16";
+  };
+
+  ###### implementation
+  config = mkIf cfg.enable {
+    services.xserver.windowManager.session = singleton {
+      name = "E16";
+      start = ''
+        ${pkgs.e16}/bin/e16 &
+        waitPID=$!
+      '';
+    };
+
+    environment.systemPackages = [ pkgs.e16 ];
+  };
+}