title: Generate a schema.json with graphql-ruby
body: <p>How can I generate a schema.json like the code in the links?</p>
  
  <p><a href="https://github.com/exAspArk/graphql-on-rails/blob/master/schema.json" rel="noreferrer">https://github.com/exAspArk/graphql-on-rails/blob/master/schema.json</a>
  <a href="https://github.com/Shopify/graphql-js-client/blob/master/schema.json" rel="noreferrer">https://github.com/Shopify/graphql-js-client/blob/master/schema.json</a></p>