Make `graphql` a peer dependency and simplify local development

[roschaefer]

@johnymontana explained to me here that I run into the error:

Error: Cannot use GraphQLObjectType "Query" from another module or realm.

because you don't have graphql as a peer dependency.

I will outline a workaround in CONTRIBUTING.md but it would be great if you could make it a peer dependency to enable yarn link and friends.

It took me some hours to find a workaround and you could make life better for a lot of people + encourage more people to contribute to this library.

[malikalimoekhamedov]

I want this so bad.

[michaeldgraham]

#608