WebSocketServer not declared in the current scope

**Your Godot version: 4.0.1 stable**

**Issue description: WebSocketServer not implemented or Document not updated**

I tried to implement a part of my work with Godot using Websocket server and client.
Godot 3.x Websocket minimal code work ok.
When changed to Godot 4.x, it seems a major change in Websocket. I could not find "WebSocketServer" in the document. The online document is an outdated version that does not work at this moment.

I got this Error when defining
`var _server = WebSocketServer.new()`

`Identifier "WebSocketServer" not declared in the current scope.`

Any suggestion?