How to maintain the ZTK versions page

The ZTK version configuration page and the linked version and requirements files are built from a special branch of the ZTK GitHub repository.

  $ git clone -b gh-pages git@github.com:zopefoundation/zopetoolkit
  $ cd zopetoolkit
  $ ./build_indexes.sh
  $ git add README.md releases/
  $ git commit -m "Add new ZTK releases."
  $ git push origin gh-pages

The end result is available at https://zopefoundation.github.io/zopetoolkit/.