Bump to 0.4.0. (#46)

Author: jmjoy

Cargo.toml

@@ -24,7 +24,7 @@ members = [
 
 [package]
 name = "skywalking"
-version = "0.3.0"
+version = "0.4.0"
 authors = ["Apache Software Foundation"]
 edition = "2021"
 description = "Apache SkyWalking Rust Agent"