Merge pull request #125 from Unity-Technologies/simulation_core_upgrade

Upgraded to simulation core 0.0.10-preview.20

com.unity.perception/package.json

     "com.unity.entities": "0.8.0-preview.8",
     "com.unity.simulation.client": "0.0.10-preview.9",
     "com.unity.simulation.capture": "0.0.10-preview.13",
-    "com.unity.simulation.core": "0.0.10-preview.19"
+    "com.unity.simulation.core": "0.0.10-preview.20"
   },
   "description": "Tools for generating large-scale data sets for perception-based machine learning training and validation",
   "displayName": "Perception",