Add animations for mood emoji selection

[danielchalmers]

Add brief 1.5-second animated visual effects when selecting mood emojis. Each emotion triggers an animation that's totally unique in style so we can try out different types. After I've tried all of them, I'll pick one to keep and re-apply it to all. For example, one might be a full overlay while another might appear in the background in iMessage-style. One might show emojis over the screen while another might show particle effects. They should match the feeling of the emoji.