Bump crate edition to 2021

Author: tnull

Cargo.toml

@@ -4,7 +4,7 @@ version = "0.1.0"
 authors = ["Elias Rohrer <dev@tnull.de>"]
 homepage = "https://lightningdevkit.org/"
 license = "MIT OR Apache-2.0"
-edition = "2018"
+edition = "2021"
 description = "A ready-to-go node implementation built using LDK."
 repository = "https://github.com/lightningdevkit/ldk-node/"
 readme = "README.md"