ci: validate renovaterc

Also use config:best-practices

.forgejo/workflows/check.yml

@@ -1,5 +1,13 @@
 on: [push]
 jobs:
+  check-renovaterc:
+    runs-on: nixos
+    steps:
+      - uses: https://git.salame.cl/actions/checkout@v4
+      - name: Validate renovaterc
+        run: |
+          nix --version
+          nix shell nixpkgs#renovate --command renovate-validate-config
   build:
     runs-on: nixos
     steps:

.renovaterc.json

@@ -9,7 +9,7 @@
   "commitBodyTable": true,
   "dependencyDashboard": true,
   "extends": [
-    "config:recommended"
+    "config:best-practices"
   ],
   "prCreation": "immediate",
   "cargo": {