Add Vulkan support on Switch

Source/Engine/Graphics/Graphics.Build.cs

@@ -76,7 +76,7 @@ public class Graphics : EngineModule
             options.PrivateDependencies.Add("GraphicsDeviceVulkan");
             break;
         case TargetPlatform.Switch:
-            options.PrivateDependencies.Add("GraphicsDeviceNull"); // TODO: use Vulkan on Switch
+            options.PrivateDependencies.Add("GraphicsDeviceVulkan");
             break;
         default: throw new InvalidPlatformException(options.Platform.Target);
         }

Source/Engine/Graphics/Graphics.cpp

@@ -171,6 +171,14 @@ bool GraphicsService::Init()
             device = CreateGPUDeviceVulkan();
 #endif
 
+#elif PLATFORM_SWITCH
+
+        // Switch
+#if GRAPHICS_API_VULKAN
+        if (!device)
+            device = CreateGPUDeviceVulkan();
+#endif
+
 #elif !defined(GRAPHICS_API_NULL)
 
 #error "Platform does not support GPU devices."