No 'description' field in _service query

Hi there @erikwrede ,

I am using graphene-federation 0.2.0 for a GQL server using graphene 2.1.9

The query string result for SDL does not contain any **description** field meta data for my types.
```
_service {
sdl
}
```

As a result, upon introspection of my subgraph in my Federated server, I lose description details in my schema.

Could **description** fields be added to the SDL? Is this supported in newer versions of the package?