Bump version to 0.4.0 (#32)

Author: shsms

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "frequenz-microgrid-component-graph"
 description = "A library for representing the components of a microgrid and the connections between them as a Directed Acyclic Graph (DAG)."
-version = "0.3.0"
+version = "0.4.0"
 edition = "2024"
 repository = "https://github.com/frequenz-floss/frequenz-microgrid-component-graph-rs"
 license = "MIT"