Add class attributes checking support

[Oreilles]

Add class attributes checking support

[jsh9]

Hi @Oreilles , thanks for submitting this issue.

From my perspective, the potential difficulty with this suggestion is: instance attributes are difficult to check.

Here's an example of "class attributes" and "instance attributes", in case there are any confusions:

class Car:
    # Class attribute
    num_wheels = 4
    
    def __init__(self, make, model):
        # Instance attributes
        self.make = make
        self.model = model

According to the Google style guide, if we are to document public attributes, we should document both class attributes and instance attributes.

The order and type hints of instance attributes are not easy to check (we may not want to enforce order anyways).

[Gabriel-p]

Came here after realizing that my dataclass attributes were not being checked. Maybe an option that can be set to enforce checking class attributes with caveats shown on screen?