Supertone Supertonic 3 model notice

AbstractVoice can optionally download the Supertonic 3 ONNX model artifacts
from:

  https://huggingface.co/Supertone/supertonic-3

Those model weights and voice-style files are not part of the default
AbstractVoice package and are licensed separately by Supertone under the
BigScience Open RAIL-M license published in that model repository:

  https://huggingface.co/Supertone/supertonic-3/blob/main/LICENSE

The minimal AbstractVoice runtime/adapter code is internal to this repository
and does not depend on the external supertonic Python SDK.
