Basic publishing targets

This example publishes only Markdown beneath doc/ and uses the generated MkDocs configuration. Generate its Makefile with perl Makefile.PL, then run make doc, make publish_build, or make publish_serve. Importing the publication adapter supplies both the documentation-maintenance and publication targets.

MkDocs is selected because no module is configured. Set MARKDOWN_PUBLISH_MODULE to try another installed engine without regenerating the Makefile.