message: add tag package-2019-12 to batch
diff: @@ -18,6 +18,7 @@ Generate all API versions currently shipped for this package
  ```yaml $(python) && $(multiapi)
  batch:
  + - tag: package-2019-12
  - tag: package-2019-11
  - tag: package-2019-09
  - tag: package-2019-08
  