The title speaks for itself. The aim is to have the NPC greet the player with a message, instead of simply presenting the list of topics. This will help give dialogues some fluff.
Prerequisite
Add a greeting property to your NPC. The greeting can be either a string or a function.

createItem("Mark", NPC(false), {
  loc: "lounge",
  properName: true,
  //greeting: "Hello"
  greeting: () => {msg("Hello"); msg("What can I do for you?")}
});

Updated npc.talkto

res.talkto = function() {
    if (!game.player.canTalk(this)) {
      return false;
    }
    if (settings.noTalkTo !== false) {
      metamsg(settings.noTalkTo);
      return false;
    }
    
    const topics = this.getTopics(this);
    if (topics.length === 0) return failedmsg(lang.no_topics, {char:game.player, item:this});

    // If the greeting property is present, we print or run the greeting before the topics
    if (this.greeting) { printOrRun(game.player, this, "greeting") }
    
    topics.push(lang.never_mind);
    if (settings.dropdownForConv) {
      showDropDown(lang.speak_to_menu_title(this), topics, function(result) {
        if (result !== lang.never_mind) {
          result.runscript();
        }
      });
    }
    else {
      showMenu(lang.speak_to_menu_title(this), topics, function(result) {
        if (result !== lang.never_mind) {
          result.runscript();
        }
      });
    }
    
    return world.SUCCESS_NO_TURNSCRIPTS;
  };