examples/app_vu Example not compliant

[mbanth]

Issues:

The app_vu example is incomplete as an App Note. It is missing a README.rst file and the doc directory, including typical contents such as the App Note text itself (i.e., ANddddd*.rst), any necessary diagrams, and an xdoc.conf file.

I have not checked the functional operation of the app_vu example.

[DaveAtkinsonXMOS]

Won't currently build for xcore.ai as it requires xcore 200 multi-channel audio board hardware.