fix(renovate): add lockFileMaintenance (#924)

The following patch adapts the renovate configuration maintain lockfiles, for
example the package-lock.json

Further information can be found in the official documentation:

https://docs.renovatebot.com/configuration-options/#lockfilemaintenance

Reviewed-on: https://gitea.com/gitea/helm-gitea/pulls/924
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Markus Pesch <markus.pesch@cryptic.systems>
Co-committed-by: Markus Pesch <markus.pesch@cryptic.systems>

renovate.json5

@@ -49,6 +49,14 @@
       ],
     },
   ],
+  lockFileMaintenance: {
+    "enabled": true,
+    "commitMessageAction": "update",
+    "commitMessageTopic": "lockfiles",
+    schedule: [
+      'at any time',
+    ]
+  },
   packageRules: [
     {
       groupName: 'subcharts (minor & patch)',