Made two controls public to use them in app.

Author: victor-david

src/Tambala.Controls/Controls/Other/LevelSlider.cs

@@ -27,7 +27,7 @@ public class LevelSlider : Slider
         /// <summary>
         /// Initializes a new instance of the <see cref="LevelSlider"/> class.
         /// </summary>
-        internal LevelSlider()
+        public LevelSlider()
         {
         }
 

src/Tambala.Controls/Controls/Other/OnOff.cs

@@ -28,7 +28,7 @@ public class OnOff : ToggleButton
         /// <summary>
         /// Initializes a new instance of the <see cref="OnOff"/> class.
         /// </summary>
-        internal OnOff()
+        public OnOff()
         {
         }