Add iOS

ios/Extensions/Collection+safe.swift

@@ -0,0 +1,18 @@
+//
+//  Collection+safe.swift
+//  Cuvent
+//
+//  Created by Marc Rousavy on 10.01.21.
+//  Copyright © 2021 Facebook. All rights reserved.
+//
+
+import Foundation
+
+extension Collection {
+  /**
+   Returns the element at the specified index if it is within bounds, otherwise nil.
+   */
+  subscript(safe index: Index) -> Element? {
+    return indices.contains(index) ? self[index] : nil
+  }
+}