Add `--ease-bounce-*` easings

[Adam Argyle]

:where(html) {
  --ease-bounce-1: linear(…);
  --ease-bounce-2: linear(…);
  --ease-bounce-3: linear(…);
  --ease-bounce-4: linear(…);
  --ease-bounce-5: linear(…);
}

see bounce in the linear-easing-generator