I see the file, but there's no way I know of to make the viewer pane play all the frames, without writing a custom plugin for it. (Or something like a codec/splitter that makes it play via the Video plugin.)
Edge actually seems to view it OK if I drag it to the browser itself. But asking Edge to open the file in the viewer pane has Edge treat it like a right-click, Save As download rather than something to display.
The animated gif plugin I wrote & released the source to could be the basis for other non-video animated formats, but the current code is very tied to some specifics of gif (especially palettes) so it wouldn't be a trivial amount of work. And the problem is none of these animated formats have taken off, while people keep bringing out more and more of them and diluting interest in the others. (And while most websites have moved to using actual video formats now, often converting gif to MP4 behind the scenes while still saying "gif" everywhere.)