Document standalone objects (without an operation/path/webhook)

Describe the problem to be solved
We use OpenAPI to describe all APIs and objects in our system. Often we have an OpenAPI definition for a particular object that isn't necessarily part of an API or Webhook request/response that we'd like to call out in our documentation. For example, our product allows customization through a lightweight python runtime that we pass deeply nested compositional objects to. I'd love to be able to use redoc to document the shape of those objects.

Describe the solution you'd like
I guess it would be an OpenAPI extension that would allow me to identify objects that I want to be documented at the top-level. They should still have tags but wouldn't have verbs. The webhooks enhancment was sort of inline with what we'd like, but they're not always webhooks either.

Describe alternatives you've considered
Using your webhook feature to document things that are not actually webooks, leading to some confusion.

Additional context

The issue names the existing webhook feature as the closest related work; start by reviewing how that feature documents top-level items. Define how standalone objects should be identified and shown with tags but without verbs, and consider how the result avoids confusing them with webhooks.