Template rendering

[ekmartin]

This is definitely a stretch goal, but if we have time we could allow request handlers to return HTML with a templating data structure similar to the nested lists e.g. Racket uses:

(send/suspend
 (lambda (k-url)
   (response/xexpr
    `(html (head (title "Enter a number"))
           (body
            (form ([action ,k-url])
                  "Enter a number: "
                  (input ([name "number"]))
                  (input ([type "submit"]))))))))