Thread composer UI (#6050)

* Basic adding of posts

* Switch active post on focus

* Conditionally show plus button

* Insert posts midthread

* Track active/inactive post

* Delete posts in a thread

* Focus after deletion

* Tweak empty post detection

* Mix height for active only

* Move toolbar with post on web

* Fix footer positioning

* Post All button

* Fix reply to positioning

* Improve memoization

* Improve memoization for clearVideo

* Remove unnecessary argument

* Add some manual memoization to fix re-renders

* Scroll to bottom on add new

* Fix opacity on Android

* Add backdrop

* Fix videos

* Check alt for video too

* Clear pending publish on error

* Fork alt message by type

* Separate placeholder for next posts

* Limit hitslop to avoid clashes

src/view/com/util/forms/DropdownButton.tsx

@@ -2,6 +2,7 @@ import React, {PropsWithChildren, useMemo, useRef} from 'react'
 import {
   Dimensions,
   GestureResponderEvent,
+  Insets,
   StyleProp,
   StyleSheet,
   TouchableOpacity,
@@ -64,6 +65,7 @@ interface DropdownButtonProps {
   openUpwards?: boolean
   rightOffset?: number
   bottomOffset?: number
+  hitSlop?: Insets
   accessibilityLabel?: string
   accessibilityHint?: string
 }
@@ -80,6 +82,7 @@ export function DropdownButton({
   openUpwards = false,
   rightOffset = 0,
   bottomOffset = 0,
+  hitSlop = HITSLOP_10,
   accessibilityLabel,
 }: PropsWithChildren<DropdownButtonProps>) {
   const {_} = useLingui()
@@ -152,7 +155,7 @@ export function DropdownButton({
         testID={testID}
         style={style}
         onPress={onPress}
-        hitSlop={HITSLOP_10}
+        hitSlop={hitSlop}
         ref={ref1}
         accessibilityRole="button"
         accessibilityLabel={