ci: test 3.6

Author: Agnes Lin

.github/workflows/continous-integration.yaml

@@ -17,7 +17,7 @@ jobs:
       matrix:
         node-version: [10, 12, 14]
         # mongodb-3.2-precise
-        mongodb-version: [3.2]
+        mongodb-version: [3.6]
 
     steps:
     - name: Git checkout