"Add to home screen" icon in iPhone

I have an Ionic 3 PWA.

The index.html:

<!doctype html>
<html lang="en" dir="ltr">

<head>

  ...

  <meta name="apple-mobile-web-app-status-bar-style" content="black">

  <!-- Home Screen Icons -->
  <link rel="apple-touch-icon" sizes="180x180" href="apple-touch-icon-iphone.png" type="image/png">
  ...
  <link rel="mask-icon" href="safari-pinned-tab.svg" color="#5bbad5">

  <!-- iOS Startup Images -->
  <link rel="apple-touch-startup-image"  href="iphone5_splash.png"
        media="(device-width: 320px) and (device-height: 568px) and (-webkit-device-pixel-ratio: 2)" />
  <link rel="apple-touch-startup-image" href="iphone6_splash.png"
        media="(device-width: 375px) and (device-height: 667px) and (-webkit-device-pixel-ratio: 2)" />
  <link rel="apple-touch-startup-image" href="iphoneplus_splash.png"
        media="(device-width: 621px) and (device-height: 1104px) and (-webkit-device-pixel-ratio: 3)" />
  <link rel="apple-touch-startup-image" href="iphonex_splash.png"
        media="(device-width: 375px) and (device-height: 812px) and (-webkit-device-pixel-ratio: 3)" />
  <link rel="apple-touch-startup-image" href="ipad_splash.png"
        media="(device-width: 768px) and (device-height: 1024px) and (-webkit-device-pixel-ratio: 2)" />
  <link rel="apple-touch-startup-image" href="ipadpro1_splash.png"
        media="(device-width: 834px) and (device-height: 1112px) and (-webkit-device-pixel-ratio: 2)" />
  <link rel="apple-touch-startup-image" href="ipadpro2_splash.png"
        media="(device-width: 1024px) and (device-height: 1366px) and (-webkit-device-pixel-ratio: 2)" />
  ...

</head>

iOS - Add to Home Screen (step 1):

iOS - Add to Home Screen (step 2):

Ref: