message: Add global fontCache
diff: #pragma once
  +#include <NAS2D/Resources/Font.h>
  #include <NAS2D/Resources/Image.h>
  #include <NAS2D/Resources/Music.h>
  #include <NAS2D/Resources/ResourceCache.h>
  #include <memory>
  +inline ResourceCache<NAS2D::Font, std::string, unsigned int> fontCache;
  inline ResourceCache<NAS2D::Image, std::string> imageCache;
  inline std::unique_ptr<NAS2D::Music> trackMars;
  