Bump socket.io from 2.3.0 to 2.4.0

Bumps [socket.io](https://github.com/socketio/socket.io) from 2.3.0 to 2.4.0.
- [Release notes](https://github.com/socketio/socket.io/releases)
- [Changelog](https://github.com/socketio/socket.io/blob/2.4.0/CHANGELOG.md)
- [Commits](https://github.com/socketio/socket.io/compare/2.3.0...2.4.0)

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -15,7 +15,7 @@
         "dotenv": "^8.2.0",
         "ejs": "^3.1.3",
         "express": "^4.17.1",
-        "socket.io": "^2.3.0"
+        "socket.io": "^2.4.0"
     },
     "devDependencies": {
         "nodemon": "^2.0.4"