Use authentication with Docker Hub (#109)

* Update config.yml

* Update config.yml

* Update config.yml

* Update config.yml

Author: Xing Han Lu

.circleci/config.yml

@@ -4,7 +4,10 @@ jobs:
     "node":
         docker:
             - image: circleci/node:8.11.3
-
+              auth:
+                  username: dashautomation
+                  password: $DASH_PAT_DOCKERHUB
+                  
         steps:
             - checkout
 
@@ -29,7 +32,10 @@ jobs:
     "python-3.6": &test-template
         docker:
             - image: circleci/python:3.6-stretch-browsers
-
+              auth:
+                  username: dashautomation
+                  password: $DASH_PAT_DOCKERHUB
+                  
         environment:
             PERCY_ENABLED: True
 
@@ -103,6 +109,10 @@ jobs:
         <<: *test-template
         docker:
             - image: circleci/python:3.7-stretch-browsers
+              auth:
+                  username: dashautomation
+                  password: $DASH_PAT_DOCKERHUB
+                  
         environment:
             PERCY_ENABLE: False
 
@@ -111,6 +121,9 @@ workflows:
     version: 2
     build:
         jobs:
-            - "python-3.6"
-            - "python-3.7"
-            - "node"
+            - "python-3.6":
+                context: dash-docker-hub
+            - "python-3.7":
+                context: dash-docker-hub
+            - "node":
+                context: dash-docker-hub