Enable animation transition on Add entry + button

[luckyrat]

We'd like something like a <v-fade-transition> or <v-fab-transition> maybe. Unfortunately we can't use a built-in transition because the search bar also animates up and away at the same time as this animation would take place, causing the y position of the + button to immediately jump down and then gradually rise irrespective of the animation effect we select for the button.

Probably we could have a custom animation that lasts the same duration as the search box and increases y at the same rate as the search bar animation. Whether we fade out the button or do a fab-style scaling or slide it out over the x-axis is almost trivial in comparison to syncing the y-axis with the search box and I don't have any strong reason to prefer one approach over another at this point.

Could be a good first issue for someone with some basic CSS animations and/or Vue knowledge.