Playground does not automatically add amp-lightbox-gallery component script

## 🐛 Bug Report

### Current behavior

Add this markup to the `body` on [playground.amp.dev](https://playground.amp.dev/):

```html

```

I expected this to automatically cause the `amp-lightbox-gallery` component to be added to the page:

```html

```

Instead nothing happens. Clicking on the image does not open a lightbox either. There is also no validation error being reported, which is also unexpected.

### Expected behavior/code

The AMP component script for `amp-lightbox-gallery` should be automatically added.