Added ChannelMixer

Editor/AssetsHelpers/BaseClasses/OutputOptionVisualProvider.cs

@@ -2,26 +2,26 @@
 
 namespace Misaki.ArtToolEditor
 {
-    public class OptionsVisualProvider
+    public abstract class OptionsVisualProvider
     {
         public object dataSource;
 
-        internal virtual VisualElement ContentOnTop()
+        public virtual VisualElement ContentOnTop()
         {
             return null;
         }
 
-        internal virtual VisualElement ContentAfterList()
+        public virtual VisualElement ContentAfterList()
         {
             return null;
         }
 
-        internal virtual VisualElement ContentBeforeButton()
+        public virtual VisualElement ContentBeforeButton()
         {
             return null;
         }
 
-        internal virtual VisualElement ContentOnBottom()
+        public virtual VisualElement ContentOnBottom()
         {
             return null;
         }