Run daily backwards-compatibility tests

Use GitHub actions to run daily compatibility checks. We might need to
change this workflow and [add a notification step][1]. According to the
[official documentation][2], only the last committer of this workflow
gets the notification emails.

[1]: https://stackoverflow.com/questions/62304258/github-actions-notifications-on-workflow-failure
[2]: https://docs.github.com/en/actions/monitoring-and-troubleshooting-workflows/monitoring-workflows/notifications-for-workflow-runs

Ticket: https://phabricator.wikimedia.org/T369276

.github/workflows/daily-bc-check.yaml

@@ -0,0 +1,28 @@
+name: Check backwards compatibility for all Banners
+
+on:
+  on:
+  schedule:
+  - cron: "0 0 * * *"
+
+jobs:
+  bc-check:
+
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        node-version: [18.x]
+        # See supported Node.js release schedule at https://nodejs.org/en/about/releases/
+
+    steps:
+    - uses: actions/checkout@v3
+    - name: Use Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v3
+      with:
+        node-version: ${{ matrix.node-version }}
+        cache: 'npm'
+    # Install packages, exact versions from package-lock.json
+    - run: npm ci
+    # Run test case that runs unit tests for all banners
+    - run: npm run test:all-banners