ci: test 4.2, 4.4

Author: Agnes Lin

.github/workflows/continous-integration.yaml

@@ -17,7 +17,7 @@ jobs:
     strategy:
       matrix:
         node-version: [10, 12, 14]
-        mongodb-version: [4.0]
+        mongodb-version: [4.2, 4.4]
 
     steps:
     - name: Git checkout