This demonstrates how to add a sub-package in a user c module, as well
as how to define the necessary qstrs and enable the feature in the build.
This is used by the unix coverage build to test this feature.
This work was funded through GitHub Sponsors.
Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
Add working example code to provide a starting point for users with files
that they can just copy, and include the modules in the coverage test to
verify the complete user C module build functionality. The cexample module
uses the code originally found in cmodules.rst, which has been updated to
reflect this and partially rewritten with more complete information.