Create instructions for serving static files from reverse proxy

Serving static files (like the generated front-end bundle) directly from reverse proxy or from a server designed primarily for serving files is faster and saves resources from the actual application server to more meaningful actions. This can be meaningful especially if a lot of users enter the application at the same time (and they will all request a "number of files").

This page could have a section for it:

https://vaadin.com/docs/latest/flow/production/reverse-proxy

In most simplest form we could just list which files from the artifact to move to apache/nginx/... or we could even provide an example buildstep as a basis for deployment automation (copies relevant files).

Listing "static content" would also help people to configure modern "smart proxies" (clouldflare etc) so that they could event geo-loadbalance those.

Start with the reverse-proxy page at https://vaadin.com/docs/latest/flow/production/reverse-proxy and review how its deployment guidance is structured. Document which artifact files can be served by Apache or nginx, and consider whether an example buildstep is appropriate. Done means the page explains the static-content setup clearly enough to support reverse proxies and smart proxies.