Don't build documentation for non-public directories

I have a bunch of my modules in my bsb project that reside in directories marked not public in my bsconfig. Ideally these would not be documented either in the output of docre.

Start by locating how docre reads bsconfig and selects directories or modules for documentation. Check how the non-public setting is represented in a bsb project, then verify that those modules are excluded from generated output while public modules remain documented.

Written by the indexing model from the issue text.