update changelog (#3975)

Author: Chris Elion

com.unity.ml-agents/CHANGELOG.md

@@ -8,9 +8,13 @@ and this project adheres to
 
 ## [1.0.1-preview] - 2020-05-19
 ### Bug Fixes
-- An issue was fixed where using `--initialize-from` would resume from the past step count. (#3962)
 #### com.unity.ml-agents (C#)
+- A bug that would cause the editor to go into a loop when a prefab was selected was fixed. (#3949)
+- BrainParameters.ToProto() no longer throws an exception if none of the fields have been set. (#3930)
 #### ml-agents / ml-agents-envs / gym-unity (Python)
+- An issue was fixed where using `--initialize-from` would resume from the past step count. (#3962)
+- The gym wrapper error for the wrong number of agents now fires more consistently, and more details
+  were added to the error message when the input dimension is wrong. (#3963)
 
 ## [1.0.0-preview] - 2020-05-06