add prelude re-export for VecDeque

src/prelude.rs

@@ -2,7 +2,7 @@ pub use crate::utils::*;
 pub use anyhow::Error;
 pub use itertools::Itertools;
 pub use std::{
-    collections::{ HashMap as M, HashSet as S },
+    collections::{ HashMap as M, HashSet as S, VecDeque as D },
     cmp::Ordering as Or,
 };