Has a web app manifest file with:
    a short_name (used on the home screen)
    a name (used in the banner)
    a 192x192 png icon (the icon declarations must include a mime type of image/png)
    a start_url that loads
Has a service worker registered on your site.
Is served over HTTPS (a requirement for using service worker).
Meets a site engagement heuristic defined by Chrome (this is regularly being changed).