[enhancement]: Support fetching lyrics from external sources

[kgarner7]

• Adds LyricsRetriever interface to fetch lyircs from external source
• Adds external lyrics/updated at MediaFile (default caching of 1 month)
• Adds lrclib agent, which fetches from lrclib.net
• Updates local agent to read lyrics from track.txt/track.lrc

[github-actions[bot]]

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• js-bundle.zip
• binaries.zip