Allow passing rules directly into the graphql function

[Cito]

This question has been asked by a user of the Python port (graphql-python/graphql-core#70):

How can we validate a query against additional custom validation rules when using the graphql() function to execute the query?

Currently, the validate() call in the graphql() function does not pass any explicit rules, so only the default rules can be used.

Should we add an optional rules arg to the GraphQLArgs type that could be used to pass in custom validation rules to the graphql() function?