Add new file structure support to create-gh-project.js script (Issue 2418 task 7)

[alflennik]

See https://github.com/w3c/aria-practices/issues/2418 for more information about the task. Note that the build will fail until the changes on the move-examples-6 branch (https://github.com/w3c/aria-practices/pull/2441) are approved and merged.