Describe the bug
Customer parameter closeOnBeforeunload by default it is true, should be false

To Reproduce

Please fill the following code example:

Socket.IO server and client version: 4.1.3

Read my post here #4040 (comment)

We would have to do a tutorial, for example a space "Optimize socket.io 4.x to behave like socket.io 2.x" and put the parameters like closeOnBeforeunload to false instead of true, and other things.

Platform:

• Device: Firefox 91.0.2
• OS: Windows 7 (x64)