Add schedule event triggers to GitHub Actions workflows

GitHub Actions workflows used to validate project content are configured to be triggered by any push or pull request
that modifies relevant files. These workflows rely on external resources such as the GitHub Actions infrastructure,
GitHub Actions actions, dependencies. Inevitably, breaking changes will occur in these resources, requiring adaptation
of the project infrastructure to fix.

If the workflow is only configured to run on changes to project files, breakage caused by external changes will only be
revealed by contributor activity. This results in confusion for the contributor who will assume the failing workflow run
was caused by the change they made. This results in inconvenience for the maintainer who must explain the situation to
the contributor and do without the benefit of the automated validation of the contribution.

For this reason, it is best practices to always configure such GitHub Actions workflows to also be triggered on a
schedule. This allows breakage to be detected and resolved before it impacts contributions.

Author: per1234

.github/workflows/check-license.yml

@@ -25,6 +25,9 @@ on:
       - "[lL][iI][cC][eE][nN][cCsS][eE]*"
       - "[oO][fF][lL]*"
       - "[pP][aA][tT][eE][nN][tT][sS]*"
+  schedule:
+    # Run periodically to catch breakage caused by external changes.
+    - cron: "0 6 * * WED"
   workflow_dispatch:
   repository_dispatch:
 

.github/workflows/check-prettier-formatting-task.yml

@@ -195,6 +195,9 @@ on:
       - "**.rviz"
       - "**.sublime-syntax"
       - "**.syntax"
+  schedule:
+    # Run periodically to catch breakage caused by external changes.
+    - cron: "0 4 * * WED"
   workflow_dispatch:
   repository_dispatch:
 

.github/workflows/check-yaml-task.yml

@@ -39,6 +39,9 @@ on:
       - "**.rviz"
       - "**.sublime-syntax"
       - "**.syntax"
+  schedule:
+    # Run periodically to catch breakage caused by external changes.
+    - cron: "0 9 * * WED"
   workflow_dispatch:
   repository_dispatch: