SDK doesn't accurately represent task types

We've recently tried using the SDK to create tasks with some more advanced properties such as `timeoutSeconds` and `pollTimeoutSeconds`. These are not present in the SDK ( and aren't very obvious in the docs either ). It's required us to do something like:
```
const task = {
...simpleTask('someRef', 'someTask', {}),
taskDefinition: {
timeoutSeconds: 300,
pollTimeoutSeconds: 300
}
}
```

It'd be great if the SDK supported these options.