add cors socket.io code example

Example 1: socket io with cors

const io = require("socket.io")(httpServer, 
  { 
  cors: {    
    origin: "*",    
    methods: ["GET", "POST"]  
  }});

Example 2: socket.io cors

const io = require("socket.io")(httpServer, {  cors: {    origin: "http://localhost:8080",    methods: ["GET", "POST"]  }});httpServer.listen(3000);