How to create animated icon for my plugin?

I see a lot of plugins have animated icons. 
I looked around the forum and saw some old posts that mentioned renaming .gif to .png and uploading it. 

When I try, it lets me upload it, but in the last step when I hit Publish, it throws an error saying icon image needs to be JPEG or PNG.

So does this mean we can no longer assign animated icons to our plugins while some old one can keep them?

Any advice is appreciated.