Adding exposition about PyMC and Arviz to the Rethinking_2 code.

[grtyvr]

Hi Folks,

I am working through Statistical Rethinking 2 and since I am more familiar with python than R I landed here. It seems to me that the book is aimed at readers who are learning R and the rethinking package for R at the same time as learning the statistics. With that type of reader in mind, but instead learning the PyMC and Arviz libraries, I have started to add in notes related to how we are doing things. Any interest in reviewing my work for inclusion in the repo?