Add option to prevent comment from being used as argument explanations

[yuanchen-zhu]

I find this library extremely useful. Thank you for your great work!

Is your feature request related to a problem? Please describe.
It would be nice to have an option to indicate only docstrings are used for argument explanations. I often have nonformal comments describing TODOs and intentions that should not be visible to the external user. Right now to stop it from showing up in the argument explanation, I need to explicitly add a docstring under it.

Describe the solution you'd like

Add an option in ArgumentParser that prevent comment from being used as argument explanation.