Dataclass attributes not documented

[edmorley]

Hi

I tried using mkgendocs with a project that uses dataclasses, however the output was missing all of the dataclass attributes.

For example, the Context dataclass here:
https://github.com/heroku/sf-functions-python/blob/3d3b16abc76bde98718fa053f1226fdc4a7052f9/salesforce_functions/context.py#L36-L41

...was documented as:

## Context
\```python 
Context()
\```


---
Information relating to the function and the Salesforce org with which it is associated.

...the org attribute is missing, and also the Context() function signature is missing all arguments present in the generated constructor.