Add an example for a custom scalar.
Add an example for a custom scalar.

xuorig/graphql-ruby,nevesenin/graphql-ruby,rmosolgo/graphql-ruby,nevesenin/graphql-ruby,rmosolgo/graphql-ruby,rmosolgo/graphql-ruby,xuorig/graphql-ruby,onlimii/graphql-ruby,rmosolgo/graphql-ruby,nevesenin/graphql-ruby,tribune/graphql-ruby,musicglue/graphql-ruby,xuorig/graphql-ruby,nevesenin/graphql-ruby