Document how to keep animating timing function constants in sync

[iamralpht]

For these values, I took the cubic bezier control points from a very old reference (someone called Robert Penner named these values, Macromedia Flash developers popularized them, now they're in Figma, unchanged), and eyeballed that we seemed to show the same output as Figma's preview viewer.

For the spring values, I took them from Figma's blog post announcing the spring timing function.

I'll make a ticket to expand the comment to explain how to keep these in sync.

Originally posted by @iamralpht in https://github.com/google/automotive-design-compose/pull/972#discussion_r1559779055