[feature request] Setting to insert docstring as Python raw text

[ldanov]

What

Setting to insert the docstring as raw text, by prepending the opening triple-quotes with 'r'.

Why

When visualizing Math with LaTex in docstring meant for Sphinx and sphinx-autodoc, "some" backslashes are interpreted by Python. See example here: https://stackoverflow.com/questions/16468397/math-expression-in-docstring-is-not-rendered-correctly-by-sphinx