What is a progressive web app?
You can include the manifest now by creating an artboard. Pasting in the manifest code into the page template. Naming the page manifest.webmanifest" and then including a link to it in your pages (using their page templates).
<link rel="manifest" href="/manifest.webmanifest">
Once you create and link to a service worker you’ll need to upload it online. It must be served over a https connection. More here.
Some or all of this could be integrated into a future release of Web Export. Comments welcome.