Add support for CUDA in piper

[edurenye]

I found this python library: https://pypi.org/project/wyoming-piper/ that lists this repo as source. But I can see is not the same repo but I guess is created by the owners of this repo (rhasspy project), so I post the issue here.

I think there should be a repo just for that library this way we could easily create PRs or fork it.

But anyway this issue is to add support for CUDA, piper supports it as you can see in the readme file (https://github.com/rhasspy/piper).
But needs to add the onnxruntime-gpu dependency and support the --cuda parameter.

[edurenye]

Related to: #37
And to: rhasspy/wyoming-addons#4