Animated Gif support

[dtonon]

Currently gif are not supported, only the first frame is shown.
I'm absolutely not a fan of lazy-animated-memes, but sometime gifs are a quick and useful way to share short/simple animation.

But first, there is a usability problem: by showing only the first frame, the poster's message could be completely misunderstood. Let's think about a GIF that starts with a provocative message, and then explains the meaning. The Gossip user will receive half the information, and this could create many problems.

@bu5hm4nn did you already check on this matter in the past?

[bu5hm4nn]

emilk/egui#1857
emilk/egui#1521
TL;DR it's possible but we need to write some code to cycle through the frames and render them at the right time. I would guess maybe 2-3 days work with testing.

[zdimension]

Just in case, support for animated GIFs has been added in emilk/egui#4620.

[bu5hm4nn]

@zdimension Thanks for the heads up.
@mikedilger I just read the code for this, it only works with egui's image loaders. We could either switch to those (I know you didn't want to use them because we might loose control over network connections) or we implement their code on top of our loader.