To add a new report, simply add a new markdown (.md) file to the reports subdirectory. You can use CommonMark flavoured markdown and it will all be turned into HTML for the webpage at the shiptest progress reports page when the file is pushed to the master branch on github.
The full listing of all progress reports, and not just the most recent ones, is located here.
The entire script is contained in the main.py file. Ask Mark before making any direct changes to it, or just make a pull request.