Add comment regarding remarkable_printer

modules/remarkable.nix

@@ -7,6 +7,8 @@ lib.mkIf config.jalr.gui.enable {
   #  settings.Out = "socket://remarkable"
   #};
 
+  # https://github.com/Evidlo/remarkable_printer needs to be
+  # installed on the reMarkable
   hardware.printers.ensurePrinters = [
     {
       name = "remarkable";