Detect query/mutation/subscription roots from schema

[dush]

I have schema that defines query,mutation and subscription root type names in schema file and does not use default names

schema {
  query: query_root
  mutation: mutation_root
  subscription: subscription_root
}

type mutation_root {...}

type query_root {...}

type subscription_root {...}

But they are not recognized by gql-generator, because it's regexes does not match those names.

Example from GraphQL spec https://spec.graphql.org/October2021/#example-e2969