Preprocessing static files

I'm sure there's a way to do this with the library, but I haven't figured out the correct approach yet. I would like to run a static file server that renders `text/*` files via template engine.

Would I do this within the static file server or handle it separately? It might seem like a small thing but I like that serveDirectoryFileServer does stuff like defaulting to `index.html` for a given directory, caching data etc. I could reimplement that, of course, but I'm a fan of elegant solutions.