chaining stats

[mjskay]

one place chaining stats could be useful: using ggdist to generate a distribution of predictive histograms and then putting a lineribbon around it

inspired by
https://twitter.com/betanalpha/status/1567197240422187008?s=20&t=cRA6zlByw_dtFYk8P715QQ

[mjskay]

Once tidyverse/ggplot2#6326 hits should be able to do this easily