Insert build oses

Author: florianbecker

.github/workflows/integrate.yml

@@ -22,7 +22,8 @@ jobs:
           ubuntu-20.04-clang-9,
           ubuntu-20.04-clang-10,
           ubuntu-20.04-clang-11,
-          windows-2016-msvc2017,
+          windows-2019-msvc2015,
+          windows-2019-msvc2017,
           windows-2019-msvc2019,
           macos-10.15-xcode-11,
           macos-10.15-xcode-11.4,