Fix merge-docs failing if nothing new to merge

.github/workflows/merge-docs.yml

@@ -12,6 +12,7 @@ jobs:
       - name: Merge docs
         run: ./mergedoc.sh
       - name: Commit merged docs
+        continue-on-error: true
         run: |
           git config --global user.name 'github-actions[bot]'
           git config --global user.email 'github-actions[bot]@users.noreply.github.com'