message: [Docs] foreach const
diff: @@ -183,7 +183,7 @@ CCF offers a member function :cpp:func:`kv::MapHandle::foreach` to iterate over
  // Outputs:
  // key: key1 - value: value1
  // key: key2 - value: value2
  - handle->foreach([](string& key, string& value) {
  + handle->foreach([](const string& key, const string& value) {
  cout << " key: " << key << " - value: " << value << endl;
  return true;
  if (/* condition*/)
  