Added conversion from ListIterator to ListConstIterator

include/ArduinoJson/Internals/ListIterator.hpp

@@ -7,6 +7,7 @@
 #pragma once
 
 #include "ListNode.hpp"
+#include "ListConstIterator.hpp"
 
 namespace ArduinoJson {
 namespace Internals {
@@ -33,6 +34,8 @@ class ListIterator {
     return *this;
   }
 
+  operator ListConstIterator<T>() const { return ListConstIterator<T>(_node); }
+
  private:
   ListNode<T> *_node;
 };