feat: Add iOS launch screen configuration

- Enabled iOS web app capability with `apple-mobile-web-app-capable` meta tag.
- Added `apple-touch-startup-image` linking to the app's logo for the launch screen.

These changes enhance the user experience for iOS users by providing a seamless launch screen during app startup.

public/index.html

@@ -38,6 +38,10 @@
             content="Boost your productivity with Visual Timer. Create various timers effortlessly, from simple basic timers to routine timers for sequential execution. | 생산성을 높여주는 비주얼 타이머. 간단한 기본 타이머부터 순서대로 실행되는 루틴 타이머까지 손쉽게 타이머를 생성하세요."
         />
         <meta name="twitter:image" content="https://do0ori.github.io/visual-timer/logo500.png" />
+
+        <!-- iOS Launch Screen Image -->
+        <meta name="apple-mobile-web-app-capable" content="yes" />
+        <link rel="apple-touch-startup-image" href="%PUBLIC_URL%/logo500.png" />
         <!--
       manifest.json provides metadata used when your web app is installed on a
       user's mobile device or desktop. See https://developers.google.com/web/fundamentals/web-app-manifest/