Fix link in Introduction guide to Defining Your Schema guide.
Fix link in Introduction guide to Defining Your Schema guide.

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