Declare nix dependency

lib.rs and events.rs already use nix; it was missing from Cargo.toml so the crate did not build.

Cargo.toml

@@ -11,6 +11,7 @@ env_logger = "0.11.1"
 futures = "0.3.30"
 itertools = "0.12.1"
 log = "0.4.20"
+nix = { version = "0.31.3", features = ["fs", "socket"] }
 nom = "7.1.3"
 nom-derive = "0.10.1"
 proc-bitfield = "0.3.1"