Add automated documentation rendering of the wxflow API

[aerorahul]

Description This PR:

• auto renders the API documentation with sphinx and should be ready to be hosted to RTD at https://wxflow.readthedocs.io/en/latest/
• does not change any source code.

This PR is an incomplete documentation and does not include all the classes and functions of the module wxflow. More work is required.

Type of change

• [X] New feature (non-breaking change which adds functionality)
• [X] This change requires a documentation update

How Has This Been Tested?

Checklist

• [ ] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] My changes need updates to the documentation. I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings
• [ ] New and existing tests pass with my changes
• [ ] Any dependent changes have been merged and published