chore: add renovate config validator to CI (#2189)

Signed-off-by: Kim Tsao <ktsao@redhat.com>

.github/workflows/renovate-checks.yaml

@@ -0,0 +1,20 @@
+name: PR Renovate Config Validator
+
+on:
+  pull_request:
+    paths:
+      - '.github/renovate.json'
+    # Renovate always uses the config from the repository default branch
+    # https://docs.renovatebot.com/configuration-options/
+    branches: [ 'main' ]
+
+jobs:
+  renovate-config-validator:
+    runs-on: ubuntu-latest
+    name: Renovate Config Validator
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+      - name: Validate config
+        # See https://docs.renovatebot.com/config-validation/
+        run: |
+          npx --yes --package renovate -- renovate-config-validator --strict .github/renovate.json