group maven plugins

See: https://github.com/renovatebot/renovate/discussions/31855

renovate.json

@@ -0,0 +1,14 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": [
+    "config:recommended"
+  ],
+  "packageRules": [
+    // Group Maven plugins.
+    {
+      "groupName": "maven plugins",
+      "groupSlug": "maven-plugins",
+      "matchPackagePatterns": [ "org\\.apache\\.maven\\.plugins\\.*" ]
+    }
+  ]
+}