Fix mutation in CallingParticipantList component

ts/util/sortByTitle.ts

@@ -0,0 +1,12 @@
+// Copyright 2020 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+interface HasTitle {
+  title: string;
+}
+
+export function sortByTitle<T extends HasTitle>(
+  arr: ReadonlyArray<T>
+): Array<T> {
+  return [...arr].sort((a, b) => a.title.localeCompare(b.title));
+}