feat: add native db demo

__database/native_db-demo/src/main.rs

@@ -0,0 +1,46 @@
+use native_db::*;
+use native_model::Model;
+use native_model::native_model;
+use serde::{Deserialize, Serialize};
+
+#[derive(Serialize, Deserialize, PartialEq, Debug)]
+#[native_model(id = 1, version = 1)]
+#[native_db]
+struct Item {
+    #[primary_key]
+    id: u32,
+    #[secondary_key]
+    name: String,
+}
+
+fn main() -> Result<(), db_type::Error> {
+    let mut builder = DatabaseBuilder::new();
+    // Initialize the model
+    builder.define::<Item>()?;
+
+    // Create a database in memory
+    let db = builder.create_in_memory()?;
+
+    // Insert data (open a read-write transaction)
+    let rw = db.rw_transaction().unwrap();
+    rw.insert(Item { id: 1, name: "red".to_string() })?;
+    rw.insert(Item { id: 2, name: "green".to_string() })?;
+    rw.insert(Item { id: 3, name: "blue".to_string() })?;
+    rw.commit()?;
+
+    // Open a read-only transaction
+    let r = db.r_transaction()?;
+    // Retrieve data with id=3 
+    let retrieve_data: Item = r.get().primary(3_u32)?.unwrap();
+    println!("data id='3': {:?}", retrieve_data);
+    // Iterate items with name starting with "red"
+    for item in r.scan().secondary::<Item>(ItemKey::name)?.start_with("red") {
+        println!("data name=\"red\": {:?}", item);
+    }
+
+    // Remove data (open a read-write transaction)
+    let rw = db.rw_transaction()?;
+    rw.remove(retrieve_data)?;
+    rw.commit()?;
+    Ok(())
+}