use authenticated Docker pulls

Author: rpkyle

.circleci/config.yml

@@ -5,7 +5,10 @@ jobs:
   test:
     working_directory: ~/dashjl 
     docker:
-      - image: plotly/julia:ci 
+      - image: plotly/julia:ci
+        auth:
+          username: dashautomation
+          password: $DASH_PAT_DOCKERHUB
         environment:
           PERCY_PARALLEL_TOTAL: '-1'
           PUPPETEER_SKIP_CHROMIUM_DOWNLOAD: 'True'
@@ -54,4 +57,5 @@ workflows:
   version: 2
   build:
     jobs:
-      - "test"
+      - "test":
+          context: dash-docker-hub