Adding additional editor versions for testing.

.yamato/environments.yml

 
 test_editors:
   - version: 2019.4.6f1
+  - version: 2020.1.3f1
+  - version: 2020.2.0a21
+  - version: 2020.1.3f1
+  - version: 2020.2.0a21
 
 publish_platforms:
   - name: win