Support autodoc_class_signature

[DatGuy1]

autodoc_class_signature

This value selects how the signature will be displayed for the class defined by autoclass directive. The possible values are:

"mixed"
Display the signature with the class name.

"separated"
Display the signature as a method.

The default is "mixed".

[chrisjsewell]

https://github.com/sphinx-extensions2/sphinx-autodoc2/blob/13933a5b25a780e03f227414d432420706962212/src/autodoc2/render/rst_.py#L58

😅