Add support for scoped-slots

[Scoped slots](https://vuejs.org/v2/guide/components-slots.html#Scoped-Slots) are pretty important for compatibility with existing Vue library such as [Vue Material](https://vuematerial.io/components/table/).

It would be great be to also support some [basic destructuring](https://vuejs.org/v2/guide/components-slots.html#Destructuring-slot-scope).