Adding a second backend spec => GraphQL

[jycouet]

I just came across this repo and find the idea great. (Thx @frederikhors for the info)

In the spec, I didn't see anything related to graphql. Would it be possible to add a second option for the backend: GraphQL?
That would ensure a good schema with best practices? With testing scripts? Performance? ...
(Of course, following features of the API)

I saw some implementation with GraphQL, does that means that they are not "compliant"?