`append-map` with `for/list` body

[jackfirth]

In racket/scribble#441, Resyntax missed an opportunity to perform this simplification:

#lang resyntax/private/refactoring-test

--------------------
#lang racket
(append-map (lambda (m)
              (for/list ([u (in-list (mapping-get chunk-groups m))])
                (list (syntax-local-introduce m) (syntax-local-introduce u))))
            chunk-mentions)
--------------------
--------------------
#lang racket
(for*/list ([m (in-list chunk-mentions)]
            [u (in-list (mapping-get chunk-groups m))])
  (list (syntax-local-introduce m) (syntax-local-introduce u)))
--------------------

It would be handy to have a rule for this.