docs: update README to add notes for preloadIndexes

Author: okaryo

README.md

@@ -1,4 +1,4 @@
-[![Test and Lint](https://github.com/okaryo/lazy_load_indexed_stack/actions/workflows/test-and-lint.yml/badge.svg)](https://github.com/okaryo/lazy_load_indexed_stack/actions/workflows/test-and-lint.yml)
+[![CI](https://github.com/okaryo/lazy_load_indexed_stack/actions/workflows/ci.yml/badge.svg)](https://github.com/okaryo/lazy_load_indexed_stack/actions/workflows/ci.yml)
 [![Pub](https://img.shields.io/pub/v/lazy_load_indexed_stack)](https://pub.dev/packages/lazy_load_indexed_stack)
 
 # lazy_load_indexed_stack
@@ -13,6 +13,10 @@ Moreover, if the widget requires API requests or database access, or has a compl
 
 Therefore, we created an extended IndexedStack that builds the required widget only when it is needed, and returns the pre-built widget when it is needed again.
 
+## Features
+* **Lazy Loading**: The main feature of `LazyLoadIndexedStack` is to build children widgets only when they are needed, reducing initial load time.
+* **Preloading**: With the `preloadIndexes` parameter, you can specify indexes of children that should be built in advance, even if they are not currently visible. This is useful for preloading widgets that are likely to be needed soon.
+
 ## Usage
 You can use `LazyLoadIndexedStack` in the same way as `IndexedStack`.
 
@@ -31,10 +35,12 @@ class _MainPageState extends State<MainPage> {
       home: Scaffold(
         body: LazyLoadIndexedStack(
           index: _index,
+          preloadIndexes: const [3],
           children: [
             Page1(),
             Page2(),
             Page3(),
+            Page4(), // index3 is preloaded
           ],
         ),
         bottomNavigationBar: BottomNavigationBar(
@@ -46,6 +52,7 @@ class _MainPageState extends State<MainPage> {
             BottomNavigationBarItem1(),
             BottomNavigationBarItem2(),
             BottomNavigationBarItem3(),
+            BottomNavigationBarItem4(),
           ],
         ),
       ),