fix: only include src

Author: decahedron1

Cargo.toml

@@ -7,6 +7,7 @@ license = "MIT"
 authors = [ "Carson M <carson@pyke.io>" ]
 description = "Proc macro-free async/await Rust streams"
 repository = "https://github.com/pykeio/async-stream-lite"
+include = ["src/"]
 
 [dependencies]
 futures-core = { version = "0.3", default-features = false }