Add option to change controller LED color (#572)

This allows the user to change the controller LED while using Ryujinx.
Useful for PS4 and PS5 controllers as an example.

You can also use a spectrum-cycling Rainbow color option, or turn the LED off for DualSense controllers.

---------

Co-authored-by: Evan Husted <greem@greemdev.net>

src/Ryujinx.Input/IGamepadDriver.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 
 namespace Ryujinx.Input
 {
@@ -33,6 +34,11 @@ namespace Ryujinx.Input
         /// <param name="id">The unique id of the gamepad</param>
         /// <returns>An instance of <see cref="IGamepad"/> associated to the gamepad id given or null if not found</returns>
         IGamepad GetGamepad(string id);
+        
+        /// <summary>
+        /// Returns an <see cref="IEnumerable{T}"/> of the connected gamepads.
+        /// </summary>
+        IEnumerable<IGamepad> GetGamepads();
 
         /// <summary>
         /// Clear the internal state of the driver.