How to: Routing Configuration
The routing configuration allows routing via a config file rather than a command. 
You need to set `-routes-config` or `ROUTES_CONFIG` env variable.
The following shows a JSON file for routes config, where `default-server` can also be `null` or omitted:

```json
{
  "default-server": "vanilla:25565",
  "mappings": {
    "vanilla.example.com": "vanilla:25565",
    "forge.example.com": "forge:25565"
  }
}
```

Sending a SIGHUP signal will cause mc-router to reload the routes config from disk. The file can also be watched for changes by setting `-routes-config-watch` or the env variable `ROUTES_CONFIG_WATCH` to "true".