[Glitch] Handle Surrogate Pairs in truncate()

Port 5c744a5d7d to glitch-soc

Signed-off-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/flavours/glitch/features/status/index.jsx

@@ -161,8 +161,9 @@ const makeMapStateToProps = () => {
 };
 
 const truncate = (str, num) => {
-  if (str.length > num) {
+  const arr = Array.from(str);
-    return str.slice(0, num) + '…';
+  if (arr.length > num) {
+    return arr.slice(0, num).join('') + '…';
   } else {
     return str;
   }