Animated GIF's become static

[MinchinWeb]

When I process animated GIF's through the plugin, they become static. It seems that Pillow should be able to resize animated images and maintain the animation, but I haven't yet figured out how to do that.

[Ecno92]

I've just checked whether this issue is still relevant. It indeed is the case as the resize method of pillow does not support resizing animated gifs out of the box.
(see also: https://stackoverflow.com/a/41755454)

It does not seem to be very complex to fix, but some help is desired.
Feel free to open a pull request.