Exclude assets from cargo release

Cargo.toml

 [package]
 name = "micro_musicbox"
-version = "0.3.2"
+version = "0.3.3"
 edition = "2021"
 license = "Apache-2.0"
 authors = ["Louis Capitanchik <louis@microhacks.co.uk>"]
@@ -8,6 +8,8 @@ repository = "https://lab.lcr.gr/microhacks/micro-bevy-musicbox"
 documentation = "https://docs.rs/micro_musicbox"
 description = "Opinionated service interface for bevy_kira_audio"
 
+exclude = ["assets"]
+
 [features]
 default = []
 serde = ["dep:serde"]