Add support for Dataloaders

[olivierlemasle]

Support for dataloaders (batching) would be very useful to solve the N+1 problem.

https://www.graphql-java.com/documentation/v14/batching/

[excitement-engineer]

I have updated the library so that dataloaders can be used in conjunction with this project. I have created release 2.0.0 with support for this. I pushed the code to the master branch already and it should be available in your project if you bump your dependency version. I will create release notes in the next few days.

For docs on how to use dataloaders see Guide