[GraphQL] - Enhance README.md

[Dunky13]

Please add documentation on - not only how to set up the package but also - how to execute queries.

Right now have to find it out ourselves. Would make the developer experience better! :)

[underfisk]

@Dunky13 This library will wrap and inject for you the graphql-request which is a third party but i'll make sure i add a quick explanation and link for people to read that package where there are plenty of examples and more context