Support listing *args and **kwargs with optionally leading * and **

Currently, *args and **kwargs are documented by their variable name:

```Python
def foo(*args, **kwargs):
    """"...

    Args:
        args: ...
        kwargs: ...
    """
```

Also allow for the following:

```Python
def foo(*args, **kwargs):
    """"...

    Args:
        *args: ...
        **kwargs: ...
    """
```
