Implement a FLAC decoder around claxon
See https://github.com/ruuda/claxon
The frame::FrameReader and metadata::MetadataReader types should be sufficient for everything we need here, assuming correctly parsed input from flacparse.
For using them, there are some ogg and mp4 examples in https://github.com/ruuda/claxon/tree/master/examples
Seems relatively straightforward.