[Feature Request] Easings

[marioparaschiv]

@react-spring/web has preset easings exported which include functions such as exponential, ease-in-out, etc.

Could this also be ported to solid-spring?

This is the export: https://github.com/pmndrs/react-spring/blob/fd65b605b85c3a24143c4ce9dd322fdfca9c66be/packages/shared/src/easings.ts