Added comments

.github/workflows/build-test.yml

@@ -289,7 +289,7 @@ jobs:
         os: [ubuntu-latest]
         ipywidgetsVersion: ['']
         isScheduled:
-          - ${{ github.event_name == 'schedule' && 'true' || '' }}
+          - ${{ github.event_name == 'schedule' && 'true' || '' }} # We need an empty value to preserve the matrix name (as we enforce mandatory tests based on names).
         # More details on includes/excludes can be found here https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#example-including-additional-values-into-combinations
         # Basically with exclude, you can exclude any of the combinations from the result matrix.
         # & with include, you can include additional items to the result matrix.