Add to Home Screen (progressive web app) functionality

Idea.

It may be good to have an option to include the "Add to Home screen" functionality into the generated HTML, so that mobile users can "install" the project.

https://developer.mozilla.org/en-US/docs/Web/Progressive_web_apps/Add_to_home_screen

This cannot be added to an HTML file I think; it'll have to require the zip option since the manifest file has to be separate

Yes, the single file won't work. Only .zip bundles.

BTW, another useful option could be to use Service Worker to cache the app assets, so the apb can work offline (as done in the Add to Home screen documentation link above). It would probably be useful both for the Add to Home screen, and without it.

Would that make loading quicker?

It would make the loading time independent of your network speed because it's loading from your computer's file system. However, it's probably not going to be immediate because reading and storing all that in memory takes some time