scroll-driven-animations: revise description for search (#2020)

This is intended to improve the findability of this feature via its
most-visible properties.

Fixes #2004
Fixes #2003
Fixes #2002

Author: ddbeck

features/scroll-driven-animations.yml

@@ -1,5 +1,5 @@
 name: Scroll-driven animations
-description: CSS scroll-driven animations are a type of CSS animations that don't run over time, but are instead driven by the user's scroll position.
+description: The `animation-timeline`, `scroll-timeline`, and `view-timeline` CSS properties advance animations based on the user's scroll position.
 spec: https://drafts.csswg.org/scroll-animations-1/
 group:
   - scrolling