Lower feedfeedback seen threshold to 0.5s (#6127)

src/view/com/util/List.web.tsx

@@ -28,7 +28,7 @@ export type ListProps<ItemT> = Omit<
 }
 export type ListRef = React.MutableRefObject<any | null> // TODO: Better types.
 
-const ON_ITEM_SEEN_WAIT_DURATION = 1.5e3 // when we consider post to  be "seen"
+const ON_ITEM_SEEN_WAIT_DURATION = 0.5e3 // when we consider post to  be "seen"
 const ON_ITEM_SEEN_INTERSECTION_OPTS = {
   rootMargin: '-200px 0px -200px 0px',
 } // post must be 200px visible to be "seen"