title: Add to home Screen propmpt not showing using manifest json
body: <p>I need to add prompt for ADD TO HOME SCREEN using manifest.json but it is not showing while my pwa score in audit is 100%</p>
  
  <p>I have dist folder like below:-</p>
  
  <p><a href="https://i.stack.imgur.com/yEkuN.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/yEkuN.png" alt="enter image description here"></a></p>
  
  <p>My Manifest json consisting below:- </p>
  
  <pre><code>{
    "name": "xyz",
    "short_name": "xyz",
    "icons": [
      {
        "src": "/xyz/static/img/icons/xy-icon-192x192.png",
        "sizes": "192x192",
        "type": "image/png"
      },
      {
        "src": "/xyz/static/img/icons/xy-icon-512x512.png",
        "sizes": "512x512",
        "type": "image/png"
      }
    ],
    "start_url": "xyz/index.html",
    "scope": ".",
    "display": "standalone",
    "background_color": "#0628b9",
    "theme_color": "#000000"
  }
  </code></pre>
  
  <p>and i am using workbox plugin for service worker and i tried with normal service worker too like below :-</p>
  
  <p>sw.js</p>
  
  <pre><code>var VERSION = '20';
  
  self.addEventListener('install', function(e) {
    e.waitUntil(caches.open(VERSION).then(cache =&gt; {
      return cache.addAll([
        'https://cfjedimaster.github.io/nomanssky/client/index.html'
      ]);
  }))
  });
  
  self.addEventListener('fetch', function(e) {
    var tryInCachesFirst = caches.open(VERSION).then(cache =&gt; {
      return cache.match(e.request).then(response =&gt; {
        if (!response) {
      return handleNoCacheMatch(e);
    }
    // Update cache record in the background
    fetchFromNetworkAndCache(e);
    // Reply with stale data
    return response
  });
  });
    e.respondWith(tryInCachesFirst);
  });
  
  self.addEventListener('activate', function(e) {
    e.waitUntil(caches.keys().then(keys =&gt; {
      return Promise.all(keys.map(key =&gt; {
        if (key !== VERSION)
      return caches.delete(key);
  }));
  }));
  });
  
  function fetchFromNetworkAndCache(e) {
    // DevTools opening will trigger these o-i-c requests, which this SW can't handle.
    // There's probaly more going on here, but I'd rather just ignore this problem. :)
    // https://github.com/paulirish/caltrainschedule.io/issues/49
    if (e.request.cache === 'only-if-cached' &amp;&amp; e.request.mode !== 'same-origin') return;
  
    return fetch(e.request).then(res =&gt; {
      // foreign requests may be res.type === 'opaque' and missing a url
      if (!res.url) return res;
    // regardless, we don't want to cache other origin's assets
    if (new URL(res.url).origin !== location.origin) return res;
  
    return caches.open(VERSION).then(cache =&gt; {
      // TODO: figure out if the content is new and therefore the page needs a reload.
      cache.put(e.request, res.clone());
    return res;
  });
  }).catch(err =&gt; console.error(e.request.url, err));
  }
  
  function handleNoCacheMatch(e) {
    return fetchFromNetworkAndCache(e);
  }
  </code></pre>
  
  <p>and my pwa score in lighthouse is 100%.
  <a href="https://i.stack.imgur.com/9vOFd.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9vOFd.png" alt="enter image description here"></a></p>
  
  <p>but i am not able to see the prompt add to home screen. </p>