Add class for #launch-chat links (#16)

* feat(chatbot-classes): add class for #launch-chat links

Since SiteImprove and other services will not work tracking anchor tags,
we append a class to each link that is targeting the #launch-chat
trigger so that it can better be tracked.

modules/ai_engine_chat/js/events.js

@@ -8,6 +8,7 @@
 document.addEventListener("DOMContentLoaded", function () {
   var launchLinks = document.querySelectorAll('a[href="#launch-chat"]');
   launchLinks.forEach(function (link) {
+    link.classList.add("ai-chatbot");
     link.addEventListener("click", function (event) {
       event.preventDefault();
       // Trigger a click on the button with id "launch-chat-modal".