Provides access to plugin 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. Note that the use of this extension by UIs violates the important principle of UI/plugin separation, and is potentially a source of many problems. Accordingly, **use of this extension is highly discouraged**, and plugins should not expect hosts to support it, since it is often impossible to do so. To support this feature the host must pass an LV2_Feature struct to LV2_Descriptor::extension_data() with URI LV2_DATA_ACCESS_URI and data pointed to an instance of LV2_Extension_Data_Feature.