feat(scroll): dd behavior support on scrollBehavior (#3351)

Co-authored-by: Eduardo San Martin Morote <posva13@gmail.com>

Author: gaetansenn

src/util/scroll.js

@@ -160,6 +160,16 @@ function scrollToPosition (shouldScroll, position) {
   }
 
   if (position) {
-    window.scrollTo(position.x, position.y)
+    // $flow-disable-line
+    if ('scrollBehavior' in document.documentElement.style) {
+      window.scrollTo({
+        left: position.x,
+        top: position.y,
+        // $flow-disable-line
+        behavior: shouldScroll.behavior
+      })
+    } else {
+      window.scrollTo(position.x, position.y)
+    }
   }
 }

types/router.d.ts

@@ -86,7 +86,7 @@ export interface NavigationFailure extends Error {
 }
 
 type Position = { x: number; y: number }
-type PositionResult = Position | { selector: string; offset?: Position } | void
+type PositionResult = Position | { selector: string; offset?: Position, behavior?: ScrollBehavior } | void
 
 export interface RouterOptions {
   routes?: RouteConfig[]