feat(Effects): Expose tweener value

Author: jcs090218

Assets/JCSUnity/Scripts/Effects/Tweener/JCS_ShaderTweener.cs

@@ -30,6 +30,7 @@ public class JCS_ShaderTweener : JCS_UnityObject
 
         /* Setter & Getter */
 
+        public JCS_ValueTweener ValueTweener { get { return this.mValueTweener; } }
         public List<string> ShaderProps { get { return mShaderProps; } set { this.mShaderProps = value; } }
 
         /* Functions */

docs/ScriptReference/Effects/Tweener/JCS_ShaderTweener.md

@@ -6,6 +6,7 @@ Can only use for `float` properties.
 
 ## Variables
 
-| Name         | Description                 |
-|:-------------|:----------------------------|
-| mShaderProps | Target shader's properties. |
+| Name          | Description                 |
+|:--------------|:----------------------------|
+| mValueTweener | Tweener implementation.     |
+| mShaderProps  | Target shader's properties. |