public function enqueueGumroadLibs(string $which = 'all')
    {
        if (($data = $this->didEnqueueLibs(__METHOD__))) {
            return $data; // Did this already.
        } // We only need to enqueue once.

        if ($which === 'all' || $which === 'overlay') {
            $data = $this->enqueueGumroadOverlayLibs();
        }
        if ($which === 'all' || $which === 'embed') {
            $data = array_merge_recursive($data ?? [], $this->enqueueGumroadEmbedLibs());
        }
        return $data = $data ?? [];
    }