Docs: Autogeneration of pytm model into docs

[fkromer]

Continuous Thread Modeling depends on pytm being as simple to use as possible. Would it help to spread the adoption of pytm if we'd auto-generate docs about the pytm model from source code.

A common approach is using mkdocs + mkdocs-material + mkdocstrings[python] which results in something like this.

This would eliminate the risk of manual docs going out of sync from source code (an important part of the pytm docs) and would complement with already existing docs.

[fkromer]

mkdocs + mkdocs-meterial would be a modern foundation for docs initially planned to add based on Sphinx.