Fixed some code issues

RGB.NET.Brushes/Decorators/IGradientDecorator.cs

@@ -1,10 +1,10 @@
-using RGB.NET.Brushes.Gradients;
-using RGB.NET.Core;
+using RGB.NET.Core;
 
 namespace RGB.NET.Brushes
 {
+    /// <inheritdoc />
     /// <summary>
-    /// Represents a basic decorator decorating a <see cref="IGradient"/>.
+    /// Represents a basic decorator decorating a <see cref="T:RGB.NET.Brushes.Gradients.IGradient" />.
     /// </summary>
     public interface IGradientDecorator : IDecorator
     { }