test: add e2e test for config validator (#6180)

e2e/package.json

@@ -3,9 +3,18 @@
   "private": true,
   "version": "0.0.0",
   "scripts": {
-    "test": "renovate --version"
+    "test": "renovate --version && renovate-config-validator"
   },
   "dependencies": {
     "renovate": "../renovate-0.0.0-semantic-release.tgz"
+  },
+  "renovate-config": {
+    "default": {
+      "extends": [
+        "config:base",
+        ":assignAndReview(rarkins)",
+        ":maintainLockFilesWeekly"
+      ]
+    }
   }
 }