[feature-request] Add support for nodejs net.blockList object in ssh2.Server

Hi

Please can you add support for the net.blockList object (added in Node 15) in the server configuration options to block unwanted connections?

I'm currently using the following code to achieve this on client connections, but it would be more efficient to pass it on to Node's server object.

```
if (blockList.check(connectionInfo.ip)) {
  client._sock.resetAndDestroy();
  return;
}
```

Niki