Make ndcli man page contents available in ndcli command

[zeromind]

Our system packages for ndcli contain man pages that are created during package build, the Python packages do not.

It would be relatively easy to make the contents of the man page available via some ndcli subcommand. This would make it easier to access documentation, even from a venv:

• At least the command documentation is being created via https://github.com/ionos-cloud/dim/blob/master/ndcli/doc/gendoc.py, which can even be done at runtime.
• The remaining sections appear to be static: https://github.com/ionos-cloud/dim/blob/master/ndcli/doc/man.rst