Adding comment for singleton message

lib/core/CustomRequestHandler.js

@@ -2,6 +2,12 @@
 
 const logger = require('../util/loggerFactory');
 
+/*
+This class handles the custom requests made to existing playwright connection.
+This is kept as Singleton class because we want to maintain a map of commands for which
+we can resolve the response once we receive from Playwright server.
+Please don't change the singleton behaviour of this class.
+*/
 class CustomRequestHandler {
   constructor() {
     if (!CustomRequestHandler.instance) {