Enable updates of lock files by default

This will make sure that not just dependency files but also the lock
files will be managed by renovatebot, which should improve the ability
to automerge changes.

config.js

@@ -10,5 +10,6 @@ module.exports = {
   onboardingConfig: {
     extends: ['config:base'],
     prConcurrentLimit: 5,
+    updateLockFiles: true
   }
 };