message: Use dictionaryToAttributes to write mine location
diff: @@ -415,9 +415,7 @@ void TileMap::serialize(NAS2D::Xml::XmlElement* element)
  for (const auto& location : mMineLocations)
  {
  - XmlElement *mine = new XmlElement("mine");
  - mine->attribute("x", location.x);
  - mine->attribute("y", location.y);
  + auto* mine = NAS2D::dictionaryToAttributes("mine", {{{"x", location.x}, {"y", location.y}}});
  getTile(location, TileMapLevel::LEVEL_SURFACE).mine()->serialize(mine);
  mines->linkEndChild(mine);
  }
  