add wal and manifest

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

mini-lsm/src/table.rs

@@ -95,6 +95,7 @@ impl FileObject {
     /// Create a new file object (day 2) and write the file to the disk (day 4).
     pub fn create(path: &Path, data: Vec<u8>) -> Result<Self> {
         std::fs::write(path, &data)?;
+        File::open(path)?.sync_all()?;
         Ok(FileObject(
             Some(File::options().read(true).write(false).open(path)?),
             data.len() as u64,