UI: Add the ability to change a DualSense/DualShock 4's LED color.

Not functional yet. This is the UI & persistence side of #572.

src/Ryujinx.Input.SDL2/SDL2Gamepad.cs

@@ -1,6 +1,7 @@
 using Ryujinx.Common.Configuration.Hid;
 using Ryujinx.Common.Configuration.Hid.Controller;
 using Ryujinx.Common.Logging;
+using SDL2;
 using System;
 using System.Collections.Generic;
 using System.Numerics;
@@ -118,6 +119,11 @@ namespace Ryujinx.Input.SDL2
                 result |= GamepadFeaturesFlag.Rumble;
             }
 
+            if (SDL_GameControllerHasLED(_gamepadHandle) == SDL_bool.SDL_TRUE)
+            {
+                result |= GamepadFeaturesFlag.Led;
+            }
+
             return result;
         }