feat(new page): finish up page on data for your package #486

A few years ago, @NickleDave started a page on data for Python packages and what to do with it. I think it's worth having someone take over and complete the page so we can merge it.

I'm going to label this issue as help wanted / sprintable in hopes that someone who enjoys thinking about data and tests can either review the current PR to get it to "good enough status" OR add to it, etc.