bugfix: add missing ReturnTypeWillChange attributes

Author: oxidmod

src/DotArray.php

@@ -289,6 +289,7 @@ public function offsetExists($key)
      * @param  int|string $key
      * @return mixed
      */
+    #[\ReturnTypeWillChange]
     public function offsetGet($key)
     {
         return $this->get($key);
@@ -356,6 +357,7 @@ public function getIterator()
      *
      * @return array
      */
+    #[\ReturnTypeWillChange]
     public function jsonSerialize()
     {
         return $this->_ITEMS;