`Query` not being extended

It seems Graphene Federation has stopped returning an SDL with `extend type Query`, and instead returns `type Query`. I'm not sure if this is intentional, but it is not compatible with some implementations of Federation Gateway.

See diff: https://github.com/graphql-python/graphene-federation/pull/4/files#diff-3111b5ad3ddd7af276c62d4c15988d6c6f3ee13f1b6eaa87725f4fe94cc65867L42-L43

_(EDIT: It seems perhaps it was never included by default)_

Other Federation implementation seems to include this, e.g. gqlgen (Go): https://github.com/99designs/gqlgen/blob/2d8673a691deffe6ddd1f4d5f013a52dc91aef91/plugin/federation/federation.go#L223, Ariadne (Python) https://github.com/apollographql/apollo-federation-subgraph-compatibility/blob/1bc1ddd56c796f2a7ff9256d279c7780dd48f582/implementations/ariadne/schema.graphql#L65

Apollo [docs](https://www.apollographql.com/docs/federation/subgraph-spec/) seems to suggest it too, but to be honest, it's not too clear. Let me know what y'all think.