Task decorator removes docstring

[kasium]

When using @task, the decorated function loses it's docstring, because internally a functools.wraps is missing here https://github.com/pyinvoke/invoke/blob/edbb0b11b92452201c6516562140a20a2502a413/invoke/tasks.py#L353-L358

Easy to fix:

@wraps(body)
 def inner(body: Callable) -> Task[T]: 
     _task = klass(body, **kwargs) 
     return _task 

[pyhedgehog]

Dupe of #555