Support custom descriptors as attributes

Problem Description

Python descriptor don't seem to be typed properly.

Steps to reproduce the behavior:

class MyDescriptor:
    def __get__(self, obj, objtype = None) -> bool:
        return False

class Test:
    @property
    def hello(self) -> int:
        """hello world"""
        return 10
    
    foo = MyDescriptor()
    """foo bar"""

The @property is properly generated in the doc as hello: int. My understanding is that @property are basically Python descriptors.

My custom descriptor is generated as def foo(unknown):. I'm not sure how other tools handle this use case, I'd have to check. I would be expecting def foo(self) -> bool: or foo: bool.

System Information

pdoc: 14.7.0
Python: 3.10.4
Platform: Windows-10-10.0.22631-SP0

Start by reproducing the example from the issue with pdoc 14.7.0 and compare the generated output for the property with the custom descriptor. Trace how pdoc represents descriptor attributes, then make the generated documentation expose the descriptor's bool return type in a consistent form such as foo(self) -> bool or foo: bool.