Header blurred banner on overscroll (take 2) (#5474)

* grow banner when overscrolling

* add blurview

* make backdrop blur as it scrolls

* add activity indicator

* use rotated spinner instead of arrow

* persist position of back button

* make back button prettier

* make blur less jarring

* Unify effects

* Tweak impl

* determine if should animate based on scroll amount

* sign comment

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Co-authored-by: Dan Abramov <dan.abramov@gmail.com>

src/view/com/util/UserBanner.tsx

@@ -202,7 +202,7 @@ const styles = StyleSheet.create({
   },
   bannerImage: {
     width: '100%',
-    height: 150,
+    height: '100%',
   },
   defaultBanner: {
     backgroundColor: '#0070ff',