Child nodes attaching to chart or graph

[ghost]

I hacked the core to extend for children, felt dirty, and decided I'd just make an issue. Just with the line graph at the moment, I feel like it would be nice to be able to:

<LineGraph className={} xAxis***={} data={[{x:1:y1},{x:2,y:2}]}>
  <CheckboxToggleForMoreDataSets /> Toggle
</LineGraph>

So it may be part of the graph's bounding box, and can be targeted with CSS.