docs: describe the shape of the data returned by the Unleash proxy
docs: describe the shape of the data returned by the Unleash proxy

This commit attempts to explain what the proxy returns in more detail,
explaining how payloads work and what the `enabled` properties mean
and how they relate to the rest of the content.

Unleash/unleash,Unleash/unleash,Unleash/unleash,Unleash/unleash