Consider creating an overall Overview section

[jerstlouis]

Currently, the draft has overview for each requirement class but not much in terms of an overall introduction.

We could include in there the table of resources and parameters proposed by João, inform the user of where to find the OpenAPI resources, and mention the Examples annex and that developers might want to start reading the annex before diving into the detailed requirements of each requirements class.

This should help making the standard easier to digest by developers.