Add schedule trigger to sketch compile workflow

Run the workflow weekly to catch compilation failures caused by external changes (e.g., Arduino Mbed OS Boards,
ArduinoCore-API).

Author: per1234

.github/workflows/compile-examples.yml

@@ -1,5 +1,6 @@
 name: Compile Examples
 
+# See: https://docs.github.com/en/actions/reference/events-that-trigger-workflows
 on:
   pull_request:
     paths:
@@ -13,6 +14,9 @@ on:
       - "library.properties"
       - "examples/**"
       - "src/**"
+  schedule:
+    # Run every Tuesday at 8 AM UTC to catch breakage caused by changes to external resources (libraries, platforms).
+    - cron: "0 8 * * TUE"
 
 env:
   SKETCHES_REPORTS_PATH: sketches-reports