Apply quit::main to main function

This makes `quit::with_code` actually work with the correct exit code.

Fixes #111.

src/main.rs

@@ -10,6 +10,7 @@ mod troubleshooter;
 mod util;
 
 #[tokio::main]
+#[quit::main]
 async fn main() {
     cli::run().await;
 }