test: add mongodb@4.x support (testing)

Author: alias-mac

.github/workflows/ci.yml

@@ -33,7 +33,7 @@ jobs:
         mongodb-version: ['4.0', '4.2', '4.4']
         # these should match the minimum peerDependencies definitions
         mongodb-types: ['3.6.20', '^3.6.20']
-        mongodb-lib: ['3.6.7', '^3.6.7']
+        mongodb-lib: ['3.6.7', '^3.6.7', '~4.0.0', '^4.0.0']
 
     env:
       NODE: ${{ matrix.node-version }}