Example of using Antora Pipeline Extensions to add Content to the Content Catalog:
$ antora -v
@antora/cli: 3.0.0-alpha.8
@antora/site-generator-default: 3.0.0-alpha.8
$ antora antora-playbook.yml --extension antora/extensions/include.js --stacktrace
$ google-chrome build/site/session/2.6/generated.html