Add missing "ws" to node.js server packages

The server would not run correctly without ws, which adds websocket
support.

Author: Olli Etuaho

server/package-lock.json

@@ -10,6 +10,7 @@
   "license": "MIT",
   "dependencies": {
     "express": "^4.16.2",
-    "optionator": "^0.8.2"
+    "optionator": "^0.8.2",
+    "ws": "^6.0.0"
   }
 }