fix: scrollSize for scroll events

Author: farfromrefug

src/collectionview/index.android.ts

@@ -404,6 +404,7 @@ export class CollectionView extends CollectionViewBase {
             object: this,
             eventName,
             scrollOffset: offset / Utils.layout.getDisplayDensity(),
+            scrollSize: (range - extent),
             scrollOffsetPercentage: offset / (range - extent),
             dx,
             dy

src/collectionview/index.ios.ts

@@ -1038,6 +1038,7 @@ export class CollectionView extends CollectionViewBase {
             object: this,
             eventName,
             scrollOffset: offset,
+            scrollSize: size,
             scrollOffsetPercentage: offset / size,
             dx,
             dy: dy + safeAreaInsetsTop