extend introspection schema to include oneOf and specifiedByURL

Author: jimmystewpot

graphql_client_cli/src/graphql/introspection_query.graphql

@@ -27,6 +27,7 @@ fragment FullType on __Type {
   kind
   name
   description
+  isOneOf
   fields(includeDeprecated: true) {
     name
     description

graphql_client_cli/src/graphql/introspection_schema.graphql

@@ -36,6 +36,12 @@ type __Type {
 
   # NON_NULL and LIST only
   ofType: __Type
+
+  # may be non-null for custom SCALAR, otherwise null.
+  specifiedByURL: String
+
+  # should be non-null for INPUT_OBJECT only
+  isOneOf: Boolean
 }
 
 type __Field {