support for rdf:List

If I have something such as following TTL:

```turtle
:me :hobbies (:first :second :third)

:first :label "hobby 1"
...
```

I think I would expect

```graphql
query {
  id
  hobbies {
    label
  }
}
```

to return

```JS
{
id: ":me",
hobbies: ["hobby 1", ...]
}
```