ci: optional visual test step

.circleci/config.yml

@@ -367,6 +367,31 @@ workflows:
           requires:
             - UNIT_TESTS
 
+  PR_OPTIONAL_VISUAL_TESTS:
+    jobs:
+      - AWAIT_APPROVAL:
+          type: approval
+      # Update hub.docker.org
+      - cypress/run:
+          name: 'E2E: PWA'
+          executor: cypress/browsers-chrome76
+          pre-steps:
+            - run: 'rm -rf ~/.yarn && npm i -g yarn && yarn -v && yarn global
+                add wait-on' # Use yarn latest
+          yarn: true
+          store_artifacts: false
+          working_directory: platform/viewer
+          build: npx cross-env QUICK_BUILD=true yarn run build
+          # start server --> verify running --> percy + chrome + cypress
+          command: yarn run test:e2e:dist
+          cache-key: 'yarn-packages-{{ checksum "yarn.lock" }}'
+          no-workspace: true # Don't persist workspace
+          post-steps:
+            - store_artifacts:
+                path: platform/viewer/cypress/screenshots
+          requires:
+            - AWAIT_APPROVAL
+
   PR_OPTIONAL_DOCKER_PUBLISH:
     jobs:
       # https://circleci.com/docs/2.0/workflows/#holding-a-workflow-for-a-manual-approval