A reference to a type in a loaded schema, wrapping a named type in the list and non-null modifiers that apply to it.
@type kind() :: :scalar | :object | :interface | :union | :enum | :input_object | :list | :non_null
@type t() :: %TypedGql.Schema.TypeRef{ kind: kind(), name: String.t() | nil, of_type: t() | nil }