geom_violinhalf: add draw_quantiles?

[MatthieuStigler]

Describe the solution you'd like
It would be great if argument draw_quantiles that is found in geom_violin could be also implemented for geom_violinhalf!

Thanks :-)

[strengejacke]

@DominiqueMakowski what do you say? I think you have implemented this function in see.

[DominiqueMakowski]

I don't think it's easy to add given the current implemention, tho to be honest we should probably rely on tidybayes for violinhalf, as it's better implemented there with a lot of possibilities (http://mjskay.github.io/tidybayes/articles/slabinterval.html)

[IndrajeetPatil]

http://mjskay.github.io/tidybayes/articles/slabinterval.html is 404.

But, I agree, we shouldn't be reinventing the wheel here if there is already a good visualization package out there that does exactly the same thing.