ssr based on spa and backup

we can build spa using react react-router and packup. if is possible to create function named "render" that take pathname as input and return html string, we can use std/http (or oak ...) to read pathname in the incoming request then call render function and return html response.
render function will be generated based on router at build time.
if this possible to generate this "render" we can build universal app on top of spa and packup in easy way.

No files, tests, or entry points are named in the issue. Start by determining how Packup currently handles React, routing, and build-time generation; the requested result is a generated render function that accepts a pathname and returns an HTML response for server-side rendering.

Written by the indexing model from the issue text.