Build/Test Tools: Post a message to #core in Slack when a workflow fails.

This adds an additional step to each GitHub Action workflow file that posts a message to #core in Slack every time a workflow run fails.

A minor test and spacing change is included in this commit in order to that messages are posted correctly and will be reverted after testing.

See #52644.

git-svn-id: https://develop.svn.wordpress.org/trunk@51511 602fd350-edb4-49c9-b593-d223f7449a82

.github/workflows/javascript-tests.yml

@@ -50,7 +50,6 @@ jobs:
   # _ Installs NPM dependencies using install-changed to hash the `package.json` file.
   # - Run the WordPress QUnit tests.
   # - Ensures version-controlled files are not modified or deleted.
-  # - todo: Configure Slack notifications for failing tests.
   test-js:
     name: QUnit Tests
     runs-on: ubuntu-latest
@@ -86,3 +85,22 @@ jobs:
 
       - name: Ensure version-controlled files are not modified or deleted
         run: git diff --exit-code
+
+  # Post workflow related status updates to Slack.
+  #
+  # When a job in this workflow fails, a message is posted to #core.
+  #
+  # This job should always require all other jobs in this workflow to complete before running.
+  slack-notifications:
+    name: Slack Notifications
+    runs-on: ubuntu-latest
+    needs: [ test-js ]
+    if: ${{ failure() && github.repository == 'WordPress/wordpress-develop' && github.event_name != 'pull_request' }}
+
+    steps:
+      - name: Post failure notification to Slack
+        uses: slackapi/slack-github-action@d5d276d7ae0f38f29322b80da9baf985cc80f8b1 # v1.15.0
+        with:
+          payload: "{\"workflow_name\":\"${{ github.workflow }}\",\"run_url\":\"https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}\"}"
+        env:
+          SLACK_WEBHOOK_URL: ${{ secrets.SLACK_GHA_WEBHOOK_URL }}