[css-overflow-3] Make new subsection for scroll-behavior and friends

Author: fantasai

css-overflow-3/Overview.bs

@@ -708,6 +708,18 @@ Expanding Clipping Bounds: the 'overflow-clip-margin' property</h3>
 	It now also affects [=scroll containers=],
 	but only to shrink the clipping edge.
 
+<h2 id=scrolling-behaviors>
+Scrolling Behaviors and Animations</h3>
+
+CSS provides several controls over how scrolling behaves when triggered.
+	* <a href="https://www.w3.org/TR/css-scroll-snap/">CSS Scroll Snap</a> allows defining "snap positions",
+		which are scroll positions to which the [=scroll container=] is biased to land.
+	* <a href="https://www.w3.org/TR/css-overscroll/">CSS Overscroll Behavior</a>
+		allows controlling what happens when scrolling past the end of the scrollable area.
+	* 'scroll-behavior', defined below, controls whether programmatic scrolling animates smoothly or not.
+
+	Note: For animating other things in conjunction with scrolling, see [[SCROLL-ANIMATIONS-1]].
+
 <h3 id=smooth-scrolling caniuse=css-scroll-behavior>
 Smooth Scrolling: the 'scroll-behavior' Property</h3>