Mosaic grid previews of images and other files, laid out by item count
The singleImagefit input is used to specify how a single image in the modern structure should be rendered and fit. The concept is similar to the Picture's object fitgallery specific behaviors.
'contain'
This forces the whole image to be fit inside the whole width of the container. The height of the image will be scaled proportionally.

'cover'
This forces the image to fit in a
Image optimization caveat

How a single image should fit in the container.