Fix constant value sliders in material graphs to not be used due to shader compilations

Source/Editor/Surface/VisjectSurface.cs

@@ -534,6 +534,11 @@ namespace FlaxEditor.Surface
         /// </summary>
         public virtual bool CanSetParameters => false;
 
+        /// <summary>
+        /// Gets a value indicating whether surface supports/allows live previewing graph modifications due to value sliders and color pickers. True by default but disabled for shader surfaces that generate and compile shader source at flight.
+        /// </summary>
+        public virtual bool CanLivePreviewValueChanges => true;
+
         /// <summary>
         /// Determines whether the specified node archetype can be used in the surface.
         /// </summary>