feat: publish scheduled posts on their pubDate with a daily build

.github/workflows/main.yml

@@ -3,6 +3,10 @@ name: Deploy to OVH VPS
 on:
   push:
     branches: [main]
+  # Daily rebuild at 07:00 Rome (summer time) publishes posts whose pubDate is today
+  schedule:
+    - cron: "0 5 * * *"
+  workflow_dispatch:
 
 jobs:
   deploy: