add weekly plublish action

.github/workflows/weekly-publish.yml

@@ -0,0 +1,30 @@
+#schedule a book publish weekly, on Sundays, by merging
+# master into the publication branch (which will then trigger the
+# deploy-book.yml action)
+
+name: "Weekly book publish"
+
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: '30 6 * * 0'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Set Git config
+      run: |
+        git config --global user.email "github-actions@example.com"
+        git config --global user.name "GitHub Actions"    
+    
+    - name: Merge master into publication
+      uses: actions/checkout@v4
+      run: |      
+          git fetch --unshallow
+          git checkout publication
+          git pull
+          git merge --no-ff master -m "Auto-merge master back to publication"
+          git push
+