Show/animate multiple thumbnails for images

## Use Case

Sometimes, a single CSV row will represent multiple timesteps. When this happens, @MFarhadloo25 would like the thumbnails of each of those timesteps to be displayed.

He initially considered making GIF thumbnails for each, but worried that it would be too distracting to parse. Instead, we could support including multiple values in the thumbnail URL column and adding a button shortcut (`,` + `.`?) to switch between alternate thumbnails.

## Solution

_Please describe your ideal solution_

## Alternatives

_Please describe any alternatives you've considered, even if you've dismissed them_