Fixes python/docs-community#67.

Add a script to read in a JSON file of data about Python releases: PEP no, branch status, release manager and date, and EOL.

The script generates:

• Two CSV files

  • One for active branches
  • One for EOL branches

• A Mermaid Gantt chart file

The CSV files are used for the tables (#884) and the Mermaid .mmd file is used for the release cycle chart:

Rather than a Sphinx extension, this is a standalone script that can be run via make version or python generate-release-cycle.py. I've also taken advantage of standard Makefile logic so the CSV and Mermaid files are regenerated when the JSON file is modified. They're also regenerated when running make html, and only if the JSON file has been modified.

Demo

https://cpython-devguide--988.org.readthedocs.build/versions/#python-release-cycle

Questions

Q1: Is this Makefile method of generating the files acceptable? If so, I'll need a hand with the Windows make.bat (I don't have Windows).

Q2: Do we want the Python script in a subdirectory?

TODO

• Test on CI for Windows and Linux