bug: akka-sample-distributed-workers-scala doesn't work with JRE17

```
Exception (java.lang.AssertionError) encountered during startup: java.lang.reflect.InaccessibleObjectException: Unable to make field private int java.io.FileDescriptor.fd accessible: module java.base does not "opens java.io" to unnamed module @41a962cf
```

We need to add instructions to `--add-open' in the README.md
