Update merge_upstream.yml

Author: Musicminion

.github/workflows/merge_upstream.yml

@@ -1,6 +1,8 @@
 name: Merge Upstream Code
 on:
   workflow_dispatch:
+  schedule:
+    - cron: '0 0 * * *'
 
 env:
   GHCR_REGISTRY: ghcr.io