Make the app a progressive web application (PWA).

• Adjust manifest.json, e.g. provide hires icon
• Optimize performance so it passes Chrome's PWA audit (Three dots / More Tools / Developer Tools / Audits).
• Make it fully responsive (may already be ok)

Read more

• https://developer.mozilla.org/en-US/docs/Web/Progressive_web_apps
• https://developers.google.com/web/progressive-web-apps/