Provides access to LV2_Descriptor::extension_data().
This extension defines a feature, LV2_Extension_Data_Feature, which provides access to LV2_Descriptor::extension_data() for plugin UIs or other potentially remote users of a plugin. To support this feature the host must pass an LV2_Feature struct to the instantiate method with URI LV2_DATA_ACCESS_URI and data pointed to an instance of LV2_Extension_Data_Feature.