Page reload websocket connection doesn't use `pathPrefix`

[corneyl]

We want to use the eleventy dev server behind a reverse proxy, utilising Nginx.

However, the websocket connection, to get notified of changes, always connects to ws://localhost and does not respect the pathPrefix. All other files are served from the pathPrefix path correctly.

What do you think about using the pathPrefix for ws connections as well?

[zachleat]

I’d be happy to merge a PR for this!