Parse option descriptions from docstrings

[Bluenix2]

Summary

As yet another API to interactions, the library could parse the docstring for description for each option. Because of its simplicity this could be done using regex, similar to how Nextcord has implemented this.

Refer to the specification for Numpydoc, Sphinx documentation and this Google docstrings example.

The code for this would be placed inside of _process_callback() together with the existing parsing of docstrings.