message: Rename type TitleChangedCallback to TitleChangeCallback
diff: @@ -20,11 +20,11 @@ public:
  void show() override;
  void update() override;
  - using TitleChangedCallback = NAS2D::Signal<Window*>;
  + using TitleChangeCallback = NAS2D::Signal<Window*>;
  void title(const std::string& title);
  const std::string& title() const { return mTitle; }
  - TitleChangedCallback& titleChanged() { return mTitleChanged; }
  + TitleChangeCallback& titleChanged() { return mTitleChanged; }
  virtual void onTitleChanged() { mTitleChanged(this); }
  @@ -45,7 +45,7 @@ private:
  const NAS2D::Image& mTitleBarRight;
  NAS2D::RectangleSkin mBody;
  - TitleChangedCallback mTitleChanged;
  + TitleChangeCallback mTitleChanged;
  std::string mTitle;
  };
  