fix(deps): update dependency socket.io to v2 [security]

Author: renovate[bot]

package.json

@@ -25,7 +25,7 @@
     "underscore": "~1.13.0",
     "express": "~4.17.0",
     "mustache": "~3.0.0",
-    "socket.io": "~1.0.1"
+    "socket.io": "~2.4.0"
   },
   "devDependencies": {
     "grunt-contrib-qunit": "0.5.2",