Add 2.13.6 into ci matrix (#342)

Author: ckipp01

.github/workflows/ci.yml

@@ -25,6 +25,7 @@ jobs:
             { version: '2.12.10' },
             { version: '2.12.9' },
             { version: '2.12.8' },
+            { version: '2.13.6' },
             { version: '2.13.5' },
             { version: '2.13.4' },
             { version: '2.13.3' },