Support `graphql` v16

## Description

[graphql](https://github.com/graphql/graphql-js) package is a peer dependency of this package and [it's configured](https://github.com/graphql/graphql-js) to support only versions up to `v15`.

Latest `graphql` package [stable version](https://github.com/graphql/graphql-js/releases) is `v16` so it would be great is this library can add support for it.