What to do with socket.io?

[MatthijsBurgh]

We allow usage of socket.io as transport layer. Though it is not included in the library. So the user should provide it him/herself.

Though it isn't tested. So I don't know whether it works.

We should clean up this situation.

Related:
#429

[EzraBrooks]

My ongoing adventures with typescript type checking seem to imply that this feature does not actually work, because the code as written doesn't compile due to a function signature mismatch

[MatthijsBurgh]

So I suggest to drop it.