Add health websocket

This is used by some of our services.

src/node/wsRouter.ts

@@ -1,6 +1,7 @@
 import * as express from "express"
 import * as expressCore from "express-serve-static-core"
 import * as http from "http"
+import Websocket from "ws"
 import * as pluginapi from "../../typings/pluginapi"
 
 export const handleUpgrade = (app: express.Express, server: http.Server): void => {
@@ -48,3 +49,5 @@ export class WebsocketRouter {
 export function Router(): WebsocketRouter {
   return new WebsocketRouter()
 }
+
+export const wss = new Websocket.Server({ noServer: true })