add wal and manifest

Signed-off-by: Alex Chi Z <iskyzh@gmail.com>

mini-lsm/src/lib.rs

@@ -3,8 +3,10 @@ pub mod compact;
 pub mod iterators;
 pub mod lsm_iterator;
 pub mod lsm_storage;
+pub mod manifest;
 pub mod mem_table;
 pub mod table;
+pub mod wal;
 
 #[cfg(test)]
 mod tests;