Add option to use thumbnail instead of viewer until user hovers ContentPreview

To enable a more performant web experience, we would like to load the thumbnail preview of a file as fast as possible, and only initialize the viewers when the user interacts with the `` element, say by hovering over it.

We'd probably want this to be customizable by the user so maybe simply having another prop like `useThumbnail`, `disableViewer`, or some sort of flag that we could remove when we want to actually use the real viewer might be good.