ci: add submodule auto update

Author: ruattd

.github/workflows/update_submodule.yml

@@ -0,0 +1,31 @@
+name: Update Submodule
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  update-main-submodule:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Main Repository
+        uses: actions/checkout@v3
+        with:
+          repository: PCL-Community/PCL2-CE
+          token: ${{ secrets.UPDATE_PAT_TOKEN }}
+          path: repo
+
+      - name: Update Submodule
+        working-directory: repo
+        run: |
+          git config user.name "github-actions"
+          git config user.email "github-actions@users.noreply.github.com"
+          git submodule update --remote PCL.Core
+          git add PCL.Core
+          if git diff --cached --quiet; then
+            echo "The submodule is already at the latest commit"
+          else
+            git commit -m "chore(submodule): update to ${{ github.sha }}"
+            git push origin HEAD:main
+          fi