Add a method to set the order of legend and chart

[Rocksheep]

trafficstars

I added a method to the abstract chart class so users can decide if they want to display the chart or the legend first. I did not know how to write a test for this so if you have any pointers for that I am willing to write some!

[maartenpaauw]

Yo! Like we discussed in a video call, I thinks it would be a nicer solution if we add a <x-wrapper/> component with multiple (named) slots; A before-chart slot, default slot (where the chart will go) and an after-chart slot.