add changelog entries for PRs that were missing them before. (#5416)

Author: Chris Elion

com.unity.ml-agents/CHANGELOG.md

@@ -12,16 +12,22 @@ and this project adheres to
 #### com.unity.ml-agents / com.unity.ml-agents.extensions (C#)
 - update Barracuda to 2.0.0-pre.3. (#5385)
 - Fixed NullReferenceException when adding Behavior Parameters with no Agent. (#5382)
+- Add stacking option in Editor for `VectorSensorComponent`. (#5376)
 #### ml-agents / ml-agents-envs / gym-unity (Python)
+- Lock cattrs dependency version to 1.6. (#5397)
 - Added a fully connected visual encoder for environments with very small image inputs. (#5351)
 - Colab notebooks illustrating the use of the Python API are now part of the repository. (#5399)
 ### Bug Fixes
 #### com.unity.ml-agents / com.unity.ml-agents.extensions (C#)
 - RigidBodySensorComponent now displays a warning if it's used in a way that won't generate useful observations. (#5387)
 - Update the documentation with a note saying that `GridSensor` does not work in 2D environments. (#5396)
+- Fixed an error where sensors would not reset properly before collecting the last observation at the end of an
+episode. (#5375)
+
 #### ml-agents / ml-agents-envs / gym-unity (Python)
 - The calculation of the target entropy of SAC with continuous actions was incorrect and has been fixed. (#5372)
 - Fixed an issue where the histogram stats would not be reported correctly in TensorBoard. (#5410)
+- Fixed error when importing models which use the ResNet encoder. (#5358)
 
 
 ## [2.0.0-exp.1] - 2021-04-22