Add `--ease-anticipate-*` easings

[argyleink]

these would be complimentary to --ease-elastic-* in that elastic easing ends with a bounce and the anticipate easings would start with a bounce. we have --ease-squish-* which bounces both sides also. so adding these easings would give folks that disney type anticipatory animation start.

this task is to add 5 more easings that should be very similar to elastic

todo:

• [ ] add 5 new props
• [ ] update docsite with new props

[argyleink]

a strong proposal by Jhey is to name it --ease-elastic-in-* 👍🏻 the only bummer is it might mean renaming the other elastic easings and creating a breaking version. i think i'm down with the tradeoff tho, cuz this looks nice:

/* today */
--ease-elastic-3
--ease-anticipate-3 (to do)
--ease-squish-3

/* proposed breaking change */
--ease-elastic-out-3
--ease-elastic-in-3
--ease-elastic-in-out-3

[argyleink]

--ease-windup-* is another contender

[argyleink]

--ease-out-elastic-3
--ease-in-elastic-3
--ease-in-out-elastic-3

[621alexl]

Working on this now for TS Open.