The Packaging and Development guide is currently undergoing a major overhaul to bring it up to date. The current state you are seeing now is a preview of this effort.
The current version is unstable (changing URLs can occur at any time) and most content is not in properly reviewed yet. Proceed with caution and be aware of technical inaccuracies.
If you are an experienced packager and would like to contribute, we would love for you to be involved! See our contribution page for details of how to join in.