Switch to using @react-spring/web internally to solve deprecation warnings

[Macil]

This project uses react-motion internally, which doesn't appear to be very maintained. We get console warnings from modern versions of React because react-motion uses deprecated React features.

The library react-spring seems very similar to react-motion and better maintained, so I plan on switching this project to using it. I'm just opening this issue here as a todo item for myself.

The main consequence to users of react-draggable-list would be that the value of the springConfig prop will be replaced with a react-spring config object, so this change would be paired with a major version bump.