🚧 directive to load/validate yaml examples

[stevenbal]

example usage in library: maykinmedia/mozilla-django-oidc-db#133
example usage in project:

TODO:

• validate that all optional fields are used?

libraries should also make use of this directive themselves to ensure the data is validated in the docs build

[stevenbal]

@swrichards I tried out your suggestion from #35 (comment) in this PR and it might indeed be a more workable solution than generating the YAML. I've used mozilla-django-oidc-db as an example: https://github.com/maykinmedia/mozilla-django-oidc-db/pull/133/files. Like you suggested we can use autodoc pydantic to show additional information for the fields