Tutorial: listening to ephys singals

[jonnew]

A tutorial for listing to ephys signals through the audio device on the computer. This issue was inspired by the this conversation:

[jonnew]

Here is a starting point with buffer settings set to match typical buffer lengths from the ephys data nodes (30 samples):

Audio starting point

```xml 30 1000 Sine 30000 1000 0 0 Generic Software on Speakers (Realtek(R) Audio) 30000 Playing ```

[cjsha]

What headstage would be best for this tutorial? I'm thinking we do it for np2 and then explain that it can be generic for other headstages. Here's an untested example using np2:

listen-ephys.bonsai.zip (attached zip file bc github doesn't accept bonsai files)

[jonnew]

Yep I think that's a good one.

[jonnew]

On the ConvertScale node, expose the gain property and and indicate that its a volume control. Also, do we need to level shift the offset binary data produced by the the Neuropixels Data node into twos complement to play nicely with audio device?

If we can convert into some type (e.g. float) that it is easier to understand in terms of volume (e.g. -1 to 1 is max) or something, then lets do that.