add support for Azure Cloud Text to Speech

[sonodave]

Feature Request

Microsoft/Azure has some good new neural net voices and can handle switching voices in the same SSML document. It would be nice to have support for Azure TTS built into tts-cli.

Azure opens a 10 minute web socket per authorized token instead of a character limit per API call.
That makes it harder to figure how much text it can actually convert in 10 minutes.