interface to the CommonMark C library

 The CommonMark module is a wrapper around the official CommonMark C
 library libcmark. It closely follows the original API.
 .
 The main module provides some entry points to parse documents and
 convenience functions for node creation. The bulk of features is
 available through CommonMark::Node objects of which the parse tree is
 made. CommonMark::Iterator is a useful class to walk through the nodes
 in a tree. CommonMark::Parser provides a push parser interface.