update cache to enable manual runs

Author: mmcky

.github/workflows/cache.yml

@@ -3,6 +3,7 @@ on:
   schedule:
     # Execute cache weekly at 3am on Monday
     - cron:  '0 3 * * 1'
+  workflow_dispatch:  # Allows manual trigger if required
 jobs:
   tests:
     runs-on: ubuntu-latest