Update ESP3D [ESP800] format.md

Author: luc-github

Memo/ESP3D [ESP800] format.md

@@ -34,6 +34,7 @@ can be in JSON or plain text
            "WebCommunication":"Synchronous",
            "WebSocketIP":"192.168.2.117",
            "WebSocketPort":"81",
+           "WebSocketSubProtocol":"webui-3",
            "Hostname":"esp3d",
            "WiFiMode":"STA",
            "WebUpdate":"Enabled",