A folder-based image gallery for Hugo

Hugo is the platform I use to publish this weblog. Occasionally I have the need to include a collection of images in a post. Mostly this comes up on other sites that I publish. Fancybox can do this; but it wasn’t immediately clear how to direct Fancybox to create a gallery of images in a page based on images in a directory. Previously, I’ve solved this in different ways, but I was anxious to find a simple shortcode-based method.