Add ISCC on audio files

[criadoperez]

[criadoperez]

Pull request #74 added the feature to generate ISCC
Pending is to add the generated file into the JSON

[denciu]

As long as we just work with Revelator there is no rush to implement this. Let's leave it in the backlog and we'll get to it later.

[denciu]

We need to clarify requirements for this one