Add visual indicator that images are uploading

[noblereign]

When adding stickers to a pack, it'd be nice if there was some sort of visual indicator that an image was uploading. Normally this is a non-issue for most circumstances, but for people on worse connections (e.g. using 4G LTE inside of a classroom [cough cough]) it can be a bit disconcerting when the app seems to get stuck.

Maybe display the sticker initially as black and white, and have it fill from bottom-up with color as the upload progresses? Perhaps maybe a Telegram-style progress bar? Heck, even a simple bar would do. Terrible mockup for your viewing pleasures:

[Liusef]

I'm lazy so it doesn't look nearly that good

[noblereign]

That's fair