Make the CI test run regularly. (#1612)

Make the CI test run for the master branch every 12 hours even with no code pushed.
diff --git a/.github/workflows/Helix-CI.yml b/.github/workflows/Helix-CI.yml
index 057e894..aa4ff40 100644
--- a/.github/workflows/Helix-CI.yml
+++ b/.github/workflows/Helix-CI.yml
@@ -4,6 +4,8 @@
 on:
   push:
     branches: [ master ]
+  schedule:
+    - cron: '0 */12 * * *'
 
 jobs:
   Merge_PR_CI: