Add PWA as an option

[h-enk]

Summary

Brief explanation of the feature.

• Progressive web apps (PWAs)

Basic example

Include a basic example or links here.

• Workbox
• googlechrome/workbox

Motivation

Why are we doing this? What use cases does it support? What is the expected outcome?

• https://github.com/h-enk/hyas/discussions/239#discussioncomment-2752860

[h-enk]

See also Simple implementation of Progressive Web Apps (PWA) on Hugo website + Minimal viable service worker

[h-enk]

See also PWABuilder