add scroll overshoot bounce animation

[Frizi]

Pull Request Description

Implements https://www.pivotaltracker.com/n/projects/2539304/stories/183390749

scroll-overshoot.mp4

Important Notes

• The overshoot bounce animation is implemented as a animation-like FRP mixin. It is currently defined using define_endpoints macro, but should be migrated to define_endpoints_2 as soon as it supports "frp mixins" - definitions that extend external networks.

Checklist

Please include the following checklist in your PR:

• The documentation has been updated if necessary.
• All code conforms to the
  Scala,
  Java,
  and
  Rust
  style guides.
• All code has been tested:
  • Unit tests have been written where possible.
  • If GUI codebase was changed: Enso GUI was tested when built using BOTH
    ./run ide build and ./run ide watch.