viewers (transform-fn?) should be able to set form metadata

[sritchie]

This came up in Slack...

q: is it possible in a form like this

(nextjournal.clerk.viewer/with-viewer
  {:transform-fn (fn [x]
                   (clerk/mark-presented x))
   :render-fn
   '(fn [form]
      (v/html
       [:div.rounded-lg.p-4.text-xs.font-sans.bg-blue-100.border-2.border-blue-200.dark:bg-slate-800.dark:border-slate-700
        form]))}
  "cake2")

to do something in transform-fn that will automatically apply

^{:nextjournal.clerk/visibility {:code :hide}}

The title of the issue hints at a more general solution, but I'm not sure how to do it!