message: Add graphql API type to descriptor format
diff: @@ -592,6 +592,9 @@ The current set of well-known and common values for this field is:
  [OpenAPI](https://swagger.io/specification/) version 2 or version 3 spec.
  - `asyncapi` - An API definition based on the
  [AsyncAPI](https://www.asyncapi.com/docs/specifications/latest/) spec.
  +- `graphql` - An API definition based on
  + [GraphQL schemas](https://spec.graphql.org/) for consuming
  + [GraphQL](https://graphql.org/) based APIs.
  - `grpc` - An API definition based on
  [Protocol Buffers](https://developers.google.com/protocol-buffers) to use with
  [gRPC](https://grpc.io/).
  