[racket] How to fit web-server/dispatchers/dispatch-files into dispatch-rules?

Hi all,

As the Racket Web Server doc shows, we can define URL dispatching rules as follows:

  (define-values (blog-dispatch blog-url)
      (dispatch-rules
       [("") list-posts]
       [("posts" (string-arg)) review-post]
       [("archive" (integer-arg) (integer-arg)) review-archive]
       [else list-posts]))

If I want to make "blog-dispatch" as the only one dispatcher, I can do this:

  (serve/servlet blog-dispatch #:servlet-regexp #rx".*")

Here's the problem - it captures all requests, including requests to static files,
which is not what I want - I'd expect that it treats requests that don't match
any rules as a request to a static file in the htdocs/ directory.

I've found the module "web-server/dispatchers/dispatch-files" that can serve static files,
but the "make" procedure in it returns a dispatcher, which cannot be passed to "dispatch-rules"
directly. How can I "convert" it to a normal request handler?

-Limbo Peng