Adds GraphQLRequest type

[NeedleInAJayStack]

This type is not used within in this package, but is useful for clients to model the standard execution request information

[paulofaria]

Do you reckon users will import the whole library just to use this single type? I was working on a client library, some time ago, that would allow users to take a schema from graphiti to create queries. However, I wasn't super happy with the results. Do you have anything in mind on that front? I can share the code I had before, if you're interested.

[NeedleInAJayStack]

Do you reckon users will import the whole library just to use this single type?

While clients could use it, I'd expect that this will be more commonly used by HTTP servers as a Decodable target. It matches the request format of the clients I've used, including Apollo JS, Apollo iOS and graphiql toolkit

Do you have anything in mind on that front?

Sounds interesting! We're currently using other clients and generating their models from the same source as our Graphiti implementation. If it's not a ton of work to share the code, I'd be willing to poke around, but I don't imagine we'll change to a different client library anytime soon.

Thanks for the thoughts!

[paulofaria]

LGTM!