Make intermediary JSON docs format externally consumable

[sean1588]

Lighthouse ask

related to: https://github.com/pulumi/registry/issues/3834

There is an ask that the JSON docs format we are planning to produce as part of our decoupling process for internal consumption via our docs site, also support being externally consumed. Therefore we need to think more carefully to consider the implications of this and define a more formal specification for the structure and think about how this needs to be maintained and versioned as changes to this structure are made in the future.