Parsing a schema

I can figure out how to parse a schema to a `[]ast.Node`, as well as converting each node to a `*ast.ObjectDefinition`. I'm now struggling to figure out how to convert those object definitions to types.

It seems I just need to implement the `Description()` method on the ObjectDefinition to convert to a `graphql.Type` - but this feels super wrong. There should be an easy way to convert between the ast and a schema.