Add support for PostgreSQL's jsonb type

Author: sshaw

lib/generators/gql/gql_generator_base.rb

@@ -19,7 +19,8 @@ def type_map
         date: 'GraphQL::Types::ISO8601Date',
         hstore: 'GraphQL::Types::JSON',
         text: 'String',
-        json: 'GraphQL::Types::JSON'
+        json: 'GraphQL::Types::JSON',
+        jsonb: 'GraphQL::Types::JSON'
       }
     end