Lack of the docinclude folder in repository

I've tried to create PDF version of the "Repository Editing and Conversion with Reposurgeon" book using the command: asciidoctor-pdf repository-editing.adoc

I got a lot of complaints like: asciidoctor: ERROR: repository-editing.adoc: line 1246: include file not found: /home/username/reposurgeon/docinclude/syntax.adoc

From the other hand on the Resource page for reposurgeon 4.32 the documentation is complete.

Please add the docinclude folder to the repository on GitLab.