jquery-free lightbox is missing lightbox element

I tried your [lightbox](https://jekyllcodex.org/without-plugin/lightbox/) (which worked well), but then read your [Ditching jQuery and Twitter Bootstrap](https://jekyllcodex.org/blog/ditching-jquery-and-twitter-bootstrap/) post and tried that lightbox. It wasn't a drop in replacement because it's not adding the lightbox div:

```patch
diff --git a/assets/lightbox.js b/assets/lightbox.js
index 7f0675d..adbea3e 100644
--- a/assets/lightbox.js
+++ b/assets/lightbox.js
@@ -80,6 +80,12 @@ function setGallery(el) {
}

document.addEventListener("DOMContentLoaded", function() {
+
+ //create lightbox div in the footer
+ var newdiv = document.createElement("div");
+ newdiv.setAttribute('id',"lightbox");
+ document.body.appendChild(newdiv);
+
//add classes to links to be able to initiate lightboxes
var elements = document.querySelectorAll('a');
elements.forEach(element => {
```

Also, maybe you should link to that lighter lightbox from the lightbox page?