Add manual trigger to CI workflow

Closes gh-9360

Author: eleftherias

.github/workflows/continuous-integration-workflow.yml

@@ -6,6 +6,7 @@ on:
       - master
   schedule:
     - cron: '0 10 * * *' # Once per day at 10am UTC
+  workflow_dispatch: # Manual trigger
 
 env:
   SLACK_WEBHOOK_URL: ${{ secrets.SLACK_WEBHOOK_URL }}