[CI] Add nightly merge workflow for gh-pages (#363)

* Added nightly merge workflow

* Fixed branch names

Author: Andrews2024

.github/workflows/nightly-merge.yml

@@ -0,0 +1,26 @@
+name: 'Nightly Merge'
+
+on:
+  push:
+    branches:
+        - main
+
+jobs:
+  nightly-merge:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v4
+      with:
+        fetch-depth: 0 # Full clone necessary for proper merge
+
+    - name: Merge main into gh-pages 
+      uses: robotology/gh-action-nightly-merge@v1.5.2
+      with:
+        stable_branch: 'main'
+        development_branch: 'gh-pages'
+        allow_ff: false
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}