maint: Add Dependabot automerge action

Author: AlejandroFernandezLuces

.github/workflows/cicd.yml

@@ -197,3 +197,24 @@ jobs:
           bot-user: ${{ secrets.PYANSYS_CI_BOT_USERNAME }}
           bot-email: ${{ secrets.PYANSYS_CI_BOT_EMAIL }}
 
+  automerge-prs:
+    name: Automerge PRs (dependabot and pre-commit.ci only)
+    runs-on: ubuntu-latest
+    needs: [build-library]
+    if: github.event_name == 'pull_request'
+    permissions:
+      contents: write
+      pull-requests: write
+    steps:
+      - name: Automerge PRs
+        uses: ansys/actions/hk-automerge-prs@c2fa7c93f6883114e0e643599431b33d29f0b13f # v10.1.4
+        with:
+          approver: ${{ secrets.PYANSYS_CI_BOT_USERNAME }}
+          approver-token: ${{ secrets.PYANSYS_CI_BOT_TOKEN }}
+
+      - name: If pre-commit PR, add assignee
+        if: startsWith(github.head_ref, 'pre-commit-ci-update-config')
+        run: gh pr edit --add-assignee pyansys-ci-bot "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GH_TOKEN: ${{ secrets.PYANSYS_CI_BOT_TOKEN }}