@daffodil/product-configurable does not provide its own driver. Instead, it hooks into extension mechanisms exposed by @daffodil/product to extend the @daffodil/product driver via a provided module.
To provide both a configurable product fragment and a configurable product transformer to the @daffodil/product Magento driver, simply import DaffConfigurableProductMagentoDriverModule into the app. Both the configurable product Magento GraphQL fragment and the associated transformer are defined by @daffodil/product-configurable/driver/magento and are provided to the @daffodil/product Magento driver through the DaffConfigurableProductMagentoDriverModule.