The visibility of the "auth" property prevents it from being updated

[krambono]

auth property is set as private and readonly.
Therefore, we can't update it as the documentation show us.

To Reproduce

Socket.IO client version: 4.0.0

Client

I get a Typescript error here :

socket.auth.token = "efgh";
socket.disconnect().connect();

Expected behavior
We should have at least a setter to update this property.

[darrachequesne]

This should be fixed by c150223.