Allow user to pass in a custom resolve info context type (#213)

src/graphql/type/definition.py

@@ -554,8 +554,9 @@ def to_kwargs(self) -> GraphQLFieldKwargs:
     def __copy__(self) -> GraphQLField:  # pragma: no cover
         return self.__class__(**self.to_kwargs())
 
+TContext = TypeVar("TContext")
 
-class GraphQLResolveInfo(NamedTuple):
+class GraphQLResolveInfo(Generic[TContext], NamedTuple):
     """Collection of information passed to the resolvers.
 
     This is always passed as the first argument to the resolvers.