configure_graphics: Add Borderless Windowed fullscreen mode

The borderless windowed fullscreen mode solves several issues with the presentation of the overlay dialogs and on-screen keyboard in exclusive fullscreen mode, and also has other benefits such as smoother gameplay, lower latency and a significant reduction in screen tearing.

Co-authored-by: Its-Rei <kupfel@gmail.com>

src/core/settings.h

@@ -139,6 +139,7 @@ struct Values {
     Setting<int> vulkan_device;
 
     Setting<u16> resolution_factor{1};
+    Setting<int> fullscreen_mode;
     Setting<int> aspect_ratio;
     Setting<int> max_anisotropy;
     Setting<bool> use_frame_limit;