Additional motion tokens

[mcoker]

I'm assuming we might want tokens for these? Are there any others? @sg00dwin @srambach

• Shake? Not sure if you have a name for it when we rotate something back and forth. For notification bell, we rotate between 30deg at 33% and -60deg at 66% of of the duration. The deg is just an angle value, so it can be written in degrees (deg), gradians (grad), radians (rad), and turns (turn) - https://developer.mozilla.org/en-US/docs/Web/CSS/angle
• Pulse - favorited icon. We scale to 1.5 at 50% of the duration. The value is either a number or percentage. 1.5 is the same as 150%. https://developer.mozilla.org/en-US/docs/Web/CSS/transform-function/scale
• Jiggle? Shake? This is for error status. In menu toggle we translate from -2px (left by 2px) at 33% and 3px (right by 3px) at 66% of the duration. It's probably better if those values were rem units?
• For the new "expand" slide/face animations, we slide by -.5rem. That just means that by default (when the expand thing is collapsed), it's moved up by 8px (-.5rem), then slides to "0" (not moved) when expanded. Then on collapse it moves back up by 8px (-.5rem)

cc @lboehling