add renovate workflow

.gitea/workflows/renovate.yml

@@ -0,0 +1,21 @@
+name: renovate
+
+on:
+  schedule:
+    - cron: "@hourly"
+  push:
+    branches:
+      - main
+
+jobs:
+  renovate:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: https://github.com/actions/checkout@v3
+      - name: Self-hosted Renovate
+        uses: https://github.com/renovatebot/github-action@v39.0.3
+        env:
+          RENOVATE_REPOSITORY_CACHE: "enabled"
+        with:
+          token: ${{ secrets.RENOVATE_TOKEN }}