add data packages and remove empty submodule

packages/data/radixtree/examples/basic_usage.rs

@@ -0,0 +1,51 @@
+use radixtree::RadixTree;
+use std::path::PathBuf;
+
+fn main() -> Result<(), radixtree::Error> {
+    // Create a temporary directory for the database
+    let db_path = std::env::temp_dir().join("radixtree_example");
+    std::fs::create_dir_all(&db_path)?;
+    
+    println!("Creating radix tree at: {}", db_path.display());
+    
+    // Create a new radix tree
+    let mut tree = RadixTree::new(db_path.to_str().unwrap(), true)?;
+    
+    // Store some data
+    println!("Storing data...");
+    tree.set("hello", b"world".to_vec())?;
+    tree.set("help", b"me".to_vec())?;
+    tree.set("helicopter", b"flying".to_vec())?;
+    
+    // Retrieve and print the data
+    let value = tree.get("hello")?;
+    println!("hello: {}", String::from_utf8_lossy(&value));
+    
+    // Update a value
+    println!("Updating value...");
+    tree.update("hello", b"updated world".to_vec())?;
+    
+    // Retrieve the updated value
+    let updated_value = tree.get("hello")?;
+    println!("hello (updated): {}", String::from_utf8_lossy(&updated_value));
+    
+    // Delete a key
+    println!("Deleting 'help'...");
+    tree.delete("help")?;
+    
+    // Try to retrieve the deleted key (should fail)
+    match tree.get("help") {
+        Ok(value) => println!("Unexpected: help still exists with value: {}", String::from_utf8_lossy(&value)),
+        Err(e) => println!("As expected, help was deleted: {}", e),
+    }
+    
+    // Clean up (optional)
+    if std::env::var("KEEP_DB").is_err() {
+        std::fs::remove_dir_all(&db_path)?;
+        println!("Cleaned up database directory");
+    } else {
+        println!("Database kept at: {}", db_path.display());
+    }
+    
+    Ok(())
+}