chore: add node 12 ci job (#504)

Author: mayurkale22

.circleci/config.yml

@@ -44,11 +44,14 @@ workflows:
           filters: *release_tags
       - node11:
           filters: *release_tags
+      - node12:
+          filters: *release_tags
       - publish_npm:
           requires:
             - node8
             - node10
             - node11
+            - node12
           filters:
             branches:
               ignore: /.*/
@@ -79,6 +82,14 @@ jobs:
       - *mongo_service
       - *redis_service
     <<: *unit_tests
+  node12:
+    docker:
+      - image: node:12
+        user: node
+        environment: *test_env
+      - *mongo_service
+      - *redis_service
+    <<: *unit_tests
   publish_npm:
     docker:
       - image: node:8