With REST we can use Swagger, RAML or other technologies to document our API and generate an HTML documentation that our consumers can read without any need of interaction with
It looks like there is now https://www.npmjs.com/package/graphql-docs
Dynamically generated documentation explorer for GraphQL schemas. It aims to provide a better overview of a schema than GraphiQL, but without querying features.
You can also generate a static documentation file based on a schema file or GraphQL endpoint:
npm install -g graphql-docs
graphql-docs-gen http://GRAPHQL_ENDPOINT documentation.html