Added a storing file example.

[Ownezx]

This is an example of loading files and playing them several times after reading issue #423. It would not make a lot of sense for larger audio as it is not streaming.

One downside of that is that, when adding operation to the saved file, the type becomes painfully long in rust as per the example : Buffered<TakeDuration<SkipDuration<Buffered<Decoder<BufReader<File>>>>>>.

I'm not really sure how to address that for now.