Merge pull request #266 from Unity-Technologies/randomizer-tag-on-enable-virtual

RandomizerTag.OnEnable is now virtual

com.unity.perception/Runtime/Randomization/Randomizers/RandomizerTag.cs

         /// OnEnable is called when this RandomizerTag is enabled, either created, instantiated, or enabled via
         /// the Unity Editor
         /// </summary>
-        protected void OnEnable()
+        protected virtual void OnEnable()
         {
             Register();
         }