fix: ensure WAL is atomic for each write batch (#84)

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

mini-lsm-starter/src/wal.rs

@@ -27,6 +27,11 @@ impl Wal {
         unimplemented!()
     }
 
+    /// Implement this in week 3, day 5.
+    pub fn put_batch(&self, _data: &[(&[u8], &[u8])]) -> Result<()> {
+        unimplemented!()
+    }
+
     pub fn sync(&self) -> Result<()> {
         unimplemented!()
     }