feat: easier websocket interface annotation (#2438)

sanic/__init__.py

@@ -4,6 +4,7 @@ from sanic.blueprints import Blueprint
 from sanic.constants import HTTPMethod
 from sanic.request import Request
 from sanic.response import HTTPResponse, html, json, text
+from sanic.server.websockets.impl import WebsocketImplProtocol as Websocket
 
 
 __all__ = (
@@ -13,6 +14,7 @@ __all__ = (
     "HTTPMethod",
     "HTTPResponse",
     "Request",
+    "Websocket",
     "html",
     "json",
     "text",