[Video] Captions and alt text (#5009)

* video settings modal in composer

* show done button on web

* rm download options

* fix logic for showing settings button

* add language picker (wip)

* subtitle list with language select

* send captions & alt text with video when posting

* style "ensure you have selected a language" text

* include aspect ratio with video

* filter out captions where the lang is not set

* rm log

* fix label and add hint

* minor scrubber fix

src/lib/strings/helpers.ts

@@ -1,3 +1,6 @@
+import {useCallback, useMemo} from 'react'
+import Graphemer from 'graphemer'
+
 export function enforceLen(
   str: string,
   len: number,
@@ -23,6 +26,21 @@ export function enforceLen(
   return str
 }
 
+export function useEnforceMaxGraphemeCount() {
+  const splitter = useMemo(() => new Graphemer(), [])
+
+  return useCallback(
+    (text: string, maxCount: number) => {
+      if (splitter.countGraphemes(text) > maxCount) {
+        return splitter.splitGraphemes(text).slice(0, maxCount).join('')
+      } else {
+        return text
+      }
+    },
+    [splitter],
+  )
+}
+
 // https://stackoverflow.com/a/52171480
 export function toHashCode(str: string, seed = 0): number {
   let h1 = 0xdeadbeef ^ seed,