readd modules removed by mistake

src/database/abstraction.rs

@@ -3,6 +3,12 @@ use crate::Result;
 
 use std::{future::Future, pin::Pin, sync::Arc};
 
+#[cfg(feature = "sled")]
+pub mod sled;
+
+#[cfg(feature = "sqlite")]
+pub mod sqlite;
+
 #[cfg(feature = "heed")]
 pub mod heed;