This contains the nng documentation for API users.

Historically, the documentation was written in asciidoc in the form of man pages.
It is automatically formatted for display on the website.

The man pages are in the "man" directory.  The reason those are separate
is that they get special treatment.  Other documentation is located here.

HOWEVER, we are converting the documentation to mdbook -- see ref/ as the top-level
of the new tree for that.