Round out Python package examples in our packaging guide

[ucodery]

This guide contains a few example repos for the purpose of showing off in the docs. These examples are not yet full python projects, and should be expanded to be such, so that they can be built and give us a sense of assurance that what we show here really works.

[lwasser]

@ucodery this is a great issue but there is not enough information for a new contributor to tackle it. Could we add more specific information to it so people know what rounding out a package specifically entails?

[ucodery]

Right now this guide has three example project meson-py, hatchling, and setuptools (none explicitly require Hatch at this time, but any can be built with Hatch). It may grow more, but only if necessary for the guide itself.

Right now they are not real projects. For example, at this time pure-setuptools has no python files. They all should be at least a buildable + installable project, and Ideally represent a real-life project (tests, lints, automation, metadata beyond minimum necessary to build). Any contributions to add new files to these projects or to make existing files more "lifelike", without reducing clarity as an example, would be welcomed.