Do nested symbols work?
I am trying to create nested symbols but html-sketchapp-cli is instead creating a separate symbol for the containing element. For example, assume this is the generated output:

```html
<div data-sketch-symbol="Container">
    <div data-sketch-symbol="Item/Red">A</div>
    <div data-sketch-symbol="Item/blue">B</div>
    <div data-sketch-symbol="Item/Green">C</div>
    <div data-sketch-symbol="Item/Brown">D</div>
    <div data-sketch-symbol="item/Cornflowerblue">E</div>
</div>
```

The current behaviour creates a separate `Container` symbol without the `Item` symbols nested within it. Is there a separate prop for the same that is undocumented?
