add renovate workflow

Signed-off-by: Daniel Ziegenberg <daniel@ziegenberg.at>

.github/renovate.json

@@ -0,0 +1,10 @@
+{
+    "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+    "branchPrefix": "test-renovate/",
+    "onboardingConfig": { "extends": ["config:base"] },
+    "onboarding": true,
+    "requireConfig": "optional", 
+    "platform": "github",
+    "includeForks": true,
+    "repositories": ["ziegenberg/opencast"]
+}

.github/workflows/renovate.yml

@@ -0,0 +1,20 @@
+name: Renovate
+
+on:
+  schedule:
+    - cron: '0/15 * * * *'
+  workflow_dispatch:
+
+
+jobs:
+  renovate:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Self-hosted Renovate
+        uses: renovatebot/github-action@v32.238.4
+        with:
+          configurationFile: .github/renovate.json
+          token: ${{ secrets.RENOVATE_TOKEN }}  # Needs the `repo:public_repo` scope