Please add flac-metadata

[kanubacode]

flac-metadata is a utility for reading metadata embedded in FLAC audio files.

https://github.com/mfiano/flac-metadata

[quicklisp]

The mismatch between the system file name (flac-read) and the system name (flac-metadata) means ASDF can't deal with it. Please leave a comment when it's in sync.

[kanubacode]

This is fixed.