Advanced example: sounddevice streaming

Is your feature request related to a problem? Please describe.

We somewhat often get questions about how to use librosa for stream-based processing of a live audio capture. The "PCEN Streaming" example gets us part of the way there, but it uses soundfile's block streaming mode and not a live device.

Describe the solution you'd like We could add an example using the sounddevice package to do a frame- or block-based processing example with callbacks or asyncio.

The main challenge in setting this up would be getting the documentation to build consistently offline. I wonder if there's a way that we could mock this in the documentation build to simulate having a live device?

As a stretch goal, it would be great if the example could generate an animated display.