ci: add renovate

Signed-off-by: Konstantin Fickel <mail@konstantinfickel.de>

.forgejo/workflows/renovate.yml

@@ -0,0 +1,19 @@
+name: Renovate
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: "45 1 * * 5"
+
+jobs:
+  renovate:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out Repository
+        uses: https://git.konstantinfickel.de/actions/checkout@v4
+
+      - name: Self-hosted Renovate
+        uses: https://git.konstantinfickel.de/actions/renovate-action@v43.0.16
+        with:
+          docker-cmd-file: .github/renovate-entrypoint.sh
+          docker-user: root
+          token: ${{ secrets.RENOVATE_TOKEN }}