add support to sending extensions

[dh94]

from my usage with graphql i found that sometimes i'd like to have additional data
sent apart from the graphql query/mutation.

this extra data can be either headers, or another json property in the request.
currently graphiql allows me only to send the graphql body,
and i can't add extra data like headers/ extra json fields.

I think it will be a great feature to be able to send these extra data parameters through graphiql.

[joelgriffith]

You can actually do this in user-land pretty easily since GraphiQL is exported as a React component. Not sure if you've seen this: https://github.com/graphql/graphiql#usage-examples, but the features you're looking to build can be done.

Also, there's this: http://toolbox.sangria-graphql.org/graphiql which does what you've described.

[dh94]

@joelgriffith awesome, thanks for the help!