Example dapch code does not work with DVOLUME=0

[remisarrailh]

Fix #3

[ericzundel]

The error you get from this sample is similar to:

Playing A-TEAM~1.WAVDVOLUME must be set to non-zero in WaveHC.h
 Not a valid WAV

FYI, this bug is present in versions published as v1.0.2 and v1.0.3 from the Arduino Cloud IDE. This makes the library that is published unusable from the Arduino Cloud IDE out of the box, but you can downgrade to version 1.0.1 and the sample will work. Looking at the changes, there don't seem to be too much other than getting docs straightened out and skipping a ton of tests. Doh, they probably don't work in ci because the code is actually broken!