Add ngrok URL to server.allowedHosts

Currently you would need to manually add the ngrok host to your vite conf, would it be possible to do it during runtime?

```
Blocked request. This host ("123456abc.ngrok-free.app") is not allowed.
To allow this host, add "123456abc.ngrok-free.app" to `server.allowedHosts` in vite.config.js.
```