Format transaction amounts on output

This might want to use the same YNAB CSV format as `convert`.

src/main.rs

@@ -171,7 +171,7 @@ async fn main() -> anyhow::Result<()> {
             };
             println!("Transactions{} in the last 30 days:", accountstr);
             for t in transactions {
-                println!("{},{},{}", t.date, t.payee, t.amount);
+                println!("{},{},{}", t.date, t.payee, t.format_amount());
             }
 
             Ok(())