Add `CachingShardStore` for batching writes to a backend `ShardStore`

shardtree/src/lib.rs

@@ -19,6 +19,7 @@ pub use self::prunable::{
     IncompleteAt, InsertionError, LocatedPrunableTree, PrunableTree, QueryError, RetentionFlags,
 };
 
+pub mod caching;
 pub mod memory;
 
 #[cfg(any(bench, test, feature = "test-dependencies"))]
@@ -364,6 +365,11 @@ impl<
         }
     }
 
+    /// Consumes this tree and returns its underlying `ShardStore`.
+    pub fn into_store(self) -> S {
+        self.store
+    }
+
     /// Returns the root address of the tree.
     pub fn root_addr() -> Address {
         Address::from_parts(Level::from(DEPTH), 0)