Bump socket.io from 2.3.0 to 3.0.0

Bumps [socket.io](https://github.com/socketio/socket.io) from 2.3.0 to 3.0.0.
- [Release notes](https://github.com/socketio/socket.io/releases)
- [Changelog](https://github.com/socketio/socket.io/blob/master/CHANGELOG.md)
- [Commits](https://github.com/socketio/socket.io/commits)

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

package.json

@@ -37,7 +37,7 @@
     "koa-static": "^5.0.0",
     "mz": "^2.7.0",
     "relative-date": "^1.1.3",
-    "socket.io": "^2.3.0",
+    "socket.io": "^3.0.0",
     "socket.io-client": "^2.3.1",
     "vue": "2.6.12",
     "vue-router": "^3.4.8",