add renovate workflow

Author: MelvinKl

.github/workflows/renovate.yaml

@@ -0,0 +1,21 @@
+name: Renovate
+
+on:
+  schedule:
+    - cron: "0 0 * * *"
+  workflow_dispatch:
+
+jobs:
+  renovate:
+    name: Renovate
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Self-hosted Renovate
+        uses: renovatebot/github-action@v40.3.5
+        env:
+          RENOVATE_REPOSITORIES: '["stackitcloud/stackit-sdk-python"]'
+          RENOVATE_ENABLED_MANAGERS: '["poetry", "github-actions"]'
+        with:
+          token: ${{ secrets.RENOVATE_TOKEN }}