message: Mark global consts as constexpr
diff: using namespace NAS2D;
  -const int LIST_ITEM_HEIGHT = 30;
  +constexpr int LIST_ITEM_HEIGHT = 30;
  static const Font* MAIN_FONT = nullptr;
  static const Font* MAIN_FONT_BOLD = nullptr;
  -static Color ITEM_COLOR{0, 185, 0};
  -static Color HIGHLIGHT_COLOR{0, 185, 0, 75};
  +static constexpr Color ITEM_COLOR{0, 185, 0};
  +static constexpr Color HIGHLIGHT_COLOR{0, 185, 0, 75};
  static int FIRST_STOP = 0;
  