Autogenerate configuration reference

[LecrisUT]

Although all settings are mapped to the python object, just to avoid possible confusion it would be nice to generate the original configuration options ¹ as well, something like

```{confval} {{ field-name }}
:type: {{ type }}
:default: {{ default }}
{{ docstring }}

Python equivalent: {{ python-name }}
```

It would help a bit with cross-referencing the options and it would work nice with tippy.

Footnotes

1. https://www.sphinx-doc.org/en/master/usage/domains/standard.html#directive-confval ↩