chore: update readme with suffix example

README.md

@@ -25,7 +25,7 @@ use std::{net::SocketAddr, path::PathBuf};
 use parenv::Environment;
 
 #[derive(Debug, Environment)]
-#[parenv(prefix = "ENV_")]
+#[parenv(prefix = "ENV_", suffix = "_ARG")]
 struct Env {
     /// The cat
     cat: Option<u8>,