Add support for Serato library format

[Holzhaus]

Serato also writes a library to USB drives. There is no real documentation, but the format has been reverse engineered:

• https://github.com/Holzhaus/serato-tags/blob/master/scripts/database_v2.py
• https://github.com/mixxxdj/mixxx/blob/main/src/library/serato/seratofeature.cpp#L154

The Serato only contains tracks listings and crates. Cues, etc are saved in the track file tags.

[Holzhaus]

FWIW I also wrote a Rust parser for this format here:

• https://github.com/Holzhaus/triseratops/blob/main/src/library/database.rs
• https://github.com/Holzhaus/triseratops/blob/main/src/library/parser.rs