engine: cut release 0.2.4

- This fixes bugs relating to `new_channel()` and `remove_channel()`
  that most likely would break your code. Upgrading is advisable!

sqa-engine/Cargo.toml

@@ -6,7 +6,7 @@ repository = "https://github.com/eeeeeta/sqa-engine"
 readme = "README.md"
 keywords = ["audio", "sqa"]
 license = "CC0-1.0"
-version = "0.2.3"
+version = "0.2.4"
 authors = ["eeeeeta <eeeeeta@users.noreply.github.com>"]
 
 [dependencies]