PixelPaint: Close tab now prompts for a save

Author: https://github.com/alexmajor 🔰
Commit: d4a0ecac31
Pull-request: https://github.com/SerenityOS/serenity/pull/10104
Issue: https://github.com/SerenityOS/serenity/issues/8064
Reviewed-by: https://github.com/TobyAsE ✅
Reviewed-by: https://github.com/bgianfo ✅

Userland/Applications/PixelPaint/MainWidget.h

@@ -35,6 +35,7 @@ public:
 
     void open_image_fd(int fd, String const& path);
     void create_default_image();
+    bool request_close();
 
 private:
     MainWidget();