[Motion] Use rootMargin instread of threshold to trigger slide in ani…

…mations (#2517)

* Use rootMargin instread of threshold to trigger slide in animations

* address review comment, remove threshold

assets/animations.js

@@ -18,7 +18,7 @@ function initializeScrollAnimationTrigger(rootEl = document) {
   if (animationTriggerElements.length === 0) return;
 
   const observer = new IntersectionObserver(onIntersection, {
-    threshold: 0.1,
+    rootMargin: '0px 0px -50px 0px',
   });
   animationTriggerElements.forEach((element) => observer.observe(element));
 }