ci: fix environment variables (#27966)

Provide environment variables for deploying docs site

(cherry picked from commit 21a0c6a)

Author: josephperrott

.github/workflows/ci.yml

@@ -292,6 +292,9 @@ jobs:
         run: yarn ci-push-deploy-docs-app
       - uses: ./.github/actions/slack
         if: ${{ failure() && github.event_name == 'push' }}
+        env:
+          CIRCLE_BRANCH: ${{ github.ref_name }}
+          CIRCLE_SHA1: ${{ github.sha }}
         with:
           JOB_NAME: 'Docs site deployment'
           SLACK_BOT_TOKEN: ${{ secrets.ANGULAR_ROBOT_SLACK_TOKEN }}