add @angular/pwa

angular.json

ngsw-config.json

package-lock.json

package.json

src/app/app.module.ts

src/assets/icons/icon-128x128.png

src/assets/icons/icon-144x144.png

src/assets/icons/icon-152x152.png

src/assets/icons/icon-192x192.png

src/assets/icons/icon-384x384.png

src/assets/icons/icon-512x512.png

src/assets/icons/icon-72x72.png

src/assets/icons/icon-96x96.png

src/index.html

src/manifest.webmanifest