fix(index): launch screen for iOS

src/index.html

@@ -15,7 +15,13 @@
   <meta name="apple-mobile-web-app-capable" content="yes">
   <meta name="apple-mobile-web-app-title" content="Ionic PWA">
   <meta name="apple-mobile-web-app-status-bar-style" content="black">
-
+  <link href="/assets/splashscreens/iphone5_splash.png" media="(device-width: 320px) and (device-height: 568px) and (-webkit-device-pixel-ratio: 2)" rel="apple-touch-startup-image" />
+  <link href="/assets/splashscreens/iphone6_splash.png" media="(device-width: 375px) and (device-height: 667px) and (-webkit-device-pixel-ratio: 2)" rel="apple-touch-startup-image" />
+  <link href="/assets/splashscreens/iphoneplus_splash.png" media="(device-width: 621px) and (device-height: 1104px) and (-webkit-device-pixel-ratio: 3)" rel="apple-touch-startup-image" />
+  <link href="/assets/splashscreens/iphonex_splash.png" media="(device-width: 375px) and (device-height: 812px) and (-webkit-device-pixel-ratio: 3)" rel="apple-touch-startup-image" />
+  <link href="/assets/splashscreens/ipad_splash.png" media="(device-width: 768px) and (device-height: 1024px) and (-webkit-device-pixel-ratio: 2)" rel="apple-touch-startup-image" />
+  <link href="/assets/splashscreens/ipadpro1_splash.png" media="(device-width: 834px) and (device-height: 1112px) and (-webkit-device-pixel-ratio: 2)" rel="apple-touch-startup-image" />
+  <link href="/assets/splashscreens/ipadpro2_splash.png" media="(device-width: 1024px) and (device-height: 1366px) and (-webkit-device-pixel-ratio: 2)" rel="apple-touch-startup-image" />
   <meta http-equiv="x-ua-compatible" content="IE=Edge">
 
   <link href="/build/app.css" rel="stylesheet">