Align MqttJs "correlationData" field type with MqttNet

### This issue is for a: (mark with an `x`)
```
- [X] bug report -> please search issues before submitting
- [ ] feature request
- [ ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)
```

### Minimal steps to reproduce
> The MqttJs correlationData field is typed as a binary and I assumed it was of type Buffer in NodeJS.

### Expected/desired behavior
> Align the TypeScript sample Command use of correlationData to match the same data type/format that is being used in the MqttNet samples.

### Language
> TypeScript