add update react pwa feature
//This from url https://stackoverflow.com/questions/56972246/how-to-update-reactjs-based-pwa-to-the-new-version
window.addEventListener('activate', function(event) {
event.waitUntil(
caches.keys().then(function(cacheNames) {
return Promise.all(
cacheNames.filter(function(cacheName) {
// Return true if you want to remove this cache,
// but remember that caches are shared across
// the whole origin
}).map(function(cacheName) {
return caches.delete(cacheName);
})
);
})
);
});