ci: run tests once a week on a timer

Author: flavorjones

.github/workflows/ci.yml

@@ -13,6 +13,8 @@ concurrency:
 
 on:
   workflow_dispatch:
+  schedule:
+    - cron: "0 8 * * 3" # At 08:00 on Wednesday # https://crontab.guru/#0_8_*_*_3
   push:
     branches:
       - main