Merge branch 'master' into release-0.11.0

.github/ISSUE_TEMPLATE/bug_report.md

 **Environment (please complete the following information):**
 - OS + version: [e.g. Windows 10]
 - _ML-Agents version_: (e.g. ML-Agents v0.8, or latest `develop` branch from source)
+- _TensorFlow version_: (you can run `pip3 show tensorflow` to get this)
 - _Environment_: (which example environment you used to reproduce the error)
 
 **NOTE:** We are unable to help reproduce bugs with custom environments.  Please attempt to reproduce your issue with one of the example environments, or provide a minimal patch to one of the environments needed to reproduce the issue.

.github/stale.yml

     - bug
     - request
     - help-wanted
+    - announcement

markdown-link-check.config.json

         {
             "pattern": "^https://developer.nvidia.com/compute/machine-learning/cudnn/secure",
             "comment": "Requires login"
+        },
+        {
+            "pattern": "^https?://bair.berkeley.edu",
+            "comment": "Temporary berkeley outage"
         }
     ]
 }