Add following aspect ratios: 16:9, 21:9, Stretch to Window

Available as a drop down within the configure graphics tab.

src/core/settings.h

@@ -429,6 +429,7 @@ struct Values {
     int vulkan_device;
 
     float resolution_factor;
+    int aspect_ratio;
     bool use_frame_limit;
     u16 frame_limit;
     bool use_disk_shader_cache;