See the repo for an explanation of the haxe-graphql project and gql2hx libraries.
This haxelib is deprecated (or onhold, awaiting someone who needs it bad enough to implement it.)
The vision for this haxelib was to be a macro library to generate types from .gql files at macro-time. For our purposes, we ended up using the NPM library to generate .hx files before envoking the Haxe compiler.