* chore: release v6.0.0
* docs: document the 6.0.0 breaking changes
cargo-semver-checks flagged four major-breaking changes in soulseek-rs-lib,
none of which carried a `!` or BREAKING CHANGE footer, so the generated
changelog had no migration note for a major bump.
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Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Michel de Graaf <michel@re-invention.nl>
