docs: deploying on Windows (#2500)
FrankenPHP runs natively on Windows since v1.12 (#2119), but the docs
don't mention it as a deployment target. This adds a "Deploying on
Windows" section to the production guide (install, running as a Windows
service with WinSW as [recommended by the Caddy
docs](https://caddyserver.com/docs/running#windows-service), graceful
reload) and a pointer to the Windows compilation instructions in the
compile docs.
Related to #2442. Follow-ups: #2501 (static/embed, see also #2503),
#2502 (macOS).
